Thanks for respon. I found the cause.

I wrote solution and test in VS IDE and their works perfectly. When i test it here it shows everything correct but when i make attempt there error. Who knows the cause of the problem?
The Error:
In file included from main.cpp:6:
./solution.cpp:5:23: warning: comparison of integers of different signs: 'int' and 'std::__cxx11::basic_string<char, std::char_traits, std::allocator >::size_type' (aka 'unsigned long') [-Wsign-compare]