Compilare: main.cpp: In function 'int main()': main.cpp:79:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < s . size () ; ++ i){ ~~^~~~~~~~~~~~~ main.cpp:55:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen (in , "r" , stdin); ^ main.cpp:56:36: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread (buff , 1 , BUFF , stdin); ^ main.cpp: In function 'int parse()': main.cpp:38:44: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread (buff , 1 , BUFF , stdin); ^ main.cpp:47:44: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread (buff , 1 , BUFF , stdin); ^