Compilare: user.cpp: In function ‘int main()’: user.cpp:42:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<mat[x].size();++i) ^ user.cpp:28:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bellmanford.in", "r", stdin); ^ user.cpp:29:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bellmanford.out", "w", stdout); ^ user.cpp: In function ‘void read(int&)’: user.cpp:12:136: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] while(buff[pos] < '0' || buff[pos] > '9'){if(buff[pos]== '-' )semn = -1; if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;} ^ user.cpp:14:139: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] while('0' <= buff[pos] && buff[pos] <= '9') {nr = nr * 10 + buff[pos] - '0';if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;} ^