CF 409B - Mysterious Language
This is one of Codeforces' April Fools problems. There is no real algorithmic input. The judge provides a special language called "Secret" through the custom invocation system. The task is to identify what that language actually is and submit a program written in that language.
Rating: 1700
Tags: *special
Solve time: 3m 58s
Verified: yes
Solution
Problem Understanding
This is one of Codeforces' April Fools problems. There is no real algorithmic input.
The judge provides a special language called "Secret" through the custom invocation system. The task is to identify what that language actually is and submit a program written in that language. When executed, the program must print the exact name of the language.
The input is empty. Nothing needs to be read.
The output is a single fixed string, the name of the mysterious language.
The challenge is not computational. The intended difficulty comes from discovering which language "Secret" corresponds to. The accepted answer for this problem is FORTRAN 77.
Since there is no input, there are no numerical constraints, no complexity concerns, and no data structures involved.
The only real edge case is output formatting. The answer is case-sensitive and contains a space and digits.
For example, printing:
Fortran 77
is wrong because the capitalization differs.
Similarly:
FORTRAN77
is wrong because the required space is missing.
The correct output is:
FORTRAN 77
Approaches
A normal competitive programming problem would require processing input and computing some result. Here there is no computation at all.
A brute-force perspective would be to try identifying the hidden language by experimenting with language features and observing how the judge behaves. That was the intended puzzle during the contest. Once the language is recognized as FORTRAN 77, the solution becomes trivial.
The key observation is that the judge does not evaluate any algorithmic logic. It only checks whether the submitted program, written in the mysterious language, prints the language's name.
After discovering that "Secret" is FORTRAN 77, the entire problem reduces to outputting a fixed string.
| Approach | Time Complexity | Space Complexity | Verdict |
|---|---|---|---|
| Brute Force Language Investigation | Not meaningful | Not meaningful | Contest discovery process |
| Output Fixed Answer | O(1) | O(1) | Accepted |
Algorithm Walkthrough
- Determine that the hidden language provided by the judge is FORTRAN 77.
- Write a FORTRAN 77 program.
- Print the exact string
"FORTRAN 77". - Terminate the program.
Why it works
The judge expects the name of the mysterious language. The hidden language is FORTRAN 77, so printing exactly "FORTRAN 77" matches the required output. Since there is no input and no additional logic, any program that prints this exact string is accepted.
Python Solution
The original problem required submission in FORTRAN 77. Since this editorial follows the standard competitive programming template, the equivalent Python representation is:
import sys
input = sys.stdin.readline
print("FORTRAN 77")
The solution contains no input handling because the test file is empty.
The only operation performed is printing the required string. There are no loops, conditions, or calculations.
The most common mistake is changing capitalization or omitting the space between FORTRAN and 77.
Worked Examples
Since the input is always empty, every execution follows the same trace.
Example 1
Input:
<empty>
| Step | Action | Output |
|---|---|---|
| 1 | Start program | |
| 2 | Print answer | FORTRAN 77 |
| 3 | Exit | FORTRAN 77 |
The trace shows that no input is consumed and the fixed answer is produced immediately.
Example 2
Input:
<empty>
| Step | Action | Output |
|---|---|---|
| 1 | Start program | |
| 2 | Print answer | FORTRAN 77 |
| 3 | Exit | FORTRAN 77 |
This demonstrates that the program's behavior is independent of any data because no data exists.
Complexity Analysis
| Measure | Complexity | Explanation |
|---|---|---|
| Time | O(1) | One print operation |
| Space | O(1) | Constant memory usage |
The solution easily fits within the time and memory limits because it performs a single constant-time output operation.
Test Cases
# helper: run solution on input string, return output string
import sys, io
def solve():
print("FORTRAN 77")
def run(inp: str) -> str:
backup_stdin = sys.stdin
backup_stdout = sys.stdout
sys.stdin = io.StringIO(inp)
out = io.StringIO()
sys.stdout = out
solve()
sys.stdin = backup_stdin
sys.stdout = backup_stdout
return out.getvalue()
# provided sample
assert run("") == "FORTRAN 77\n", "sample 1"
# custom cases
assert run("") == "FORTRAN 77\n", "empty input"
assert run("\n") == "FORTRAN 77\n", "extra newline ignored"
assert run("random text\n") == "FORTRAN 77\n", "input is irrelevant"
assert run("1 2 3\n4 5 6\n") == "FORTRAN 77\n", "still fixed output"
| Test input | Expected output | What it validates |
|---|---|---|
| Empty input | FORTRAN 77 | Official scenario |
| Single newline | FORTRAN 77 | No dependence on input content |
| Random text | FORTRAN 77 | Output is fixed |
| Multiple lines | FORTRAN 77 | Program ignores all input |
Edge Cases
The first subtle case is capitalization.
Input:
<empty>
If a solution prints:
Fortran 77
it is rejected because the required output is case-sensitive. The algorithm handles this by printing the exact constant:
FORTRAN 77
The second subtle case is spacing.
Input:
<empty>
Printing:
FORTRAN77
is incorrect because the expected answer contains a space between the word and the number. The solution hardcodes the exact accepted string, avoiding formatting mistakes.
The final edge case is assuming input exists.
Input:
<empty>
A program that attempts to read mandatory data may fail or behave unexpectedly. The accepted solution performs no input processing and directly prints the answer, which matches the problem's specification.