Compilare: user.cpp: In function ‘int main()’: user.cpp:75:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < C.size(); i++) ^ user.cpp:77:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < C[i].size(); j++) printf("%i ", C[i][j]); ^ user.cpp:58:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.in", "r", stdin); ^ user.cpp:59:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out", "w", stdout); ^ user.cpp:61:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i %i", &N, &M); ^ user.cpp:64:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i %i", &X, &Y); ^