Compilare: user.cpp: In function ‘int main()’: user.cpp:26:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (input[i] == 'a' && i < input.size()) i++; ~~^~~~~~~~~~~~~~ user.cpp:27:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < input.size(); i++) { ~~^~~~~~~~~~~~~~ user.cpp:34:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (input[i] == 'b' && i < input.size()) i++; ~~^~~~~~~~~~~~~~ user.cpp:35:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < input.size(); i++) { ~~^~~~~~~~~~~~~~ user.cpp:42:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (input[i] == 'c' && i < input.size()) i++; ~~^~~~~~~~~~~~~~ user.cpp:43:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < input.size(); i++) { ~~^~~~~~~~~~~~~~ user.cpp:14:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("entropy.in", "r", stdin); ^ user.cpp:15:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("entropy.out", "w", stdout); ^