Compilare: main.cpp: In function 'int main()': main.cpp:98:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < G[x.second].size(); ++j) ~~^~~~~~~~~~~~~~~~~~~~ main.cpp: In function 'void read(int&)': main.cpp:32:39: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(ch, 1, bsize, stdin); ^ main.cpp:43:39: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(ch, 1, bsize, stdin); ^ main.cpp: In function 'int main()': main.cpp:52:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("gminmax.in", "r", stdin); ^ main.cpp:53:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("gminmax.out", "w", stdout); ^ main.cpp:55:31: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(ch, 1, bsize, stdin); ^