Compilare: user.cpp: In function ‘int solve(int)’: user.cpp:37:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( my_set.count( make_pair( V1, V2 )) >= K ) ^ user.cpp: In function ‘int main()’: user.cpp:46:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "substr.in" , "r", stdin ); ^ user.cpp:47:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "substr.out", "w", stdout ); ^ user.cpp:49:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf( "%d %d %s", &N, &K, S ); ^