Compilare: user.c: In function ‘main’: user.c:29:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.in","r",stdin),freopen("domino.out","w",stdout),scanf("%d\n",&n); ^ user.c:29:43: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.in","r",stdin),freopen("domino.out","w",stdout),scanf("%d\n",&n); ^ user.c:29:74: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.in","r",stdin),freopen("domino.out","w",stdout),scanf("%d\n",&n); ^ user.c:31:13: warning: ignoring return value of ‘gets’, declared with attribute warn_unused_result [-Wunused-result] gets(r),h[10*(r[0]-'0')+(r[2]-'0')][f[10*(r[0]-'0')+(r[2]-'0')]++]=i; ^ /tmp/ccx1aTR9.o: In function `main': user.c:(.text.startup+0x80): warning: the `gets' function is dangerous and should not be used.