Compilare: user.c: In function ‘main’: user.c:11:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cerere.in","r",stdin),freopen("cerere.out","w",stdout),scanf("%d\n",&n),gets(s); ^ user.c:11:43: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cerere.in","r",stdin),freopen("cerere.out","w",stdout),scanf("%d\n",&n),gets(s); ^ user.c:11:74: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("cerere.in","r",stdin),freopen("cerere.out","w",stdout),scanf("%d\n",&n),gets(s); ^ user.c:11:90: warning: ignoring return value of ‘gets’, declared with attribute warn_unused_result [-Wunused-result] freopen("cerere.in","r",stdin),freopen("cerere.out","w",stdout),scanf("%d\n",&n),gets(s); ^ user.c:18:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",a+i,b+i),w[a[i]]++,t[b[i]]=a[i]; ^ /tmp/ccoMsJrm.o: In function `main': user.c:(.text.startup+0x6f): warning: the `gets' function is dangerous and should not be used.