Compilare: user.cpp: In function ‘int Pairup(int)’: user.cpp:20:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < V[x].size(); ++ i) ^ user.cpp: In function ‘void read()’: user.cpp:49:49: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] while (S[pos] > '9' || S[pos] < '0' && pos <= l) ^ user.cpp:32:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("senat.in", "r", stdin); ^ user.cpp:33:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n%d\n", &n, &m); ^ user.cpp:37:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(S + 1); ^ user.cpp: In function ‘void write()’: user.cpp:77:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("senat.out", "w", stdout); ^ /tmp/ccMiZeLd.o: In function `read()': user.cpp:(.text+0x297): warning: the `gets' function is dangerous and should not be used.