Language: C++

%23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A

Compiler output:
a.cc:1:24: error: exponent has no digits
    1 | %23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A
      |                        ^~
a.cc:1:174: error: exponent has no digits
    1 | %23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A
      |                                                                                                                                                                              ^~
a.cc:1:177: error: exponent has no digits
    1 | %23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A
      |                                                                                                                                                                                 ^~~~
a.cc:1:183: error: exponent has no digits
    1 | %23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A
      |                                                                                                                                                                                       ^~
a.cc:1:186: error: exponent has no digits
    1 | %23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A
      |                                                                                                                                                                                          ^~~~
a.cc:1:1: error: expected unqualified-id before '%' token
    1 | %23include+%3Ciostream%3E%0A%0Ausing+namespace+std%3B%0A%0Aint+main%28%29+%7B%0A++ios%3A%3Async_with_stdio%28false%29%3B%0A++cin.tie%280%29%3B%0A%0A++int+a%2C+b%3B%0A++cin+%3E%3E+a+%3E%3E+b%3B%0A++if+%28a+%2B+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2B%22+%3C%3C+endl%3B%0A++%7D+else+if+%28a+%2A+b+%3D%3D+15%29+%7B%0A++++cout+%3C%3C+%22%2A%22+%3C%3C+endl%3B%0A++%7D+else+%7B%0A++++cout+%3C%3C+%22x%22+%3C%3C+endl%3B%0A++%7D%0A++return+0%3B%0A%7D%0A
      | ^