Compilare: user.c: In function ‘main’: user.c:4:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("alee.in","r",stdin),freopen("alee.out","w",stdout),scanf("%d%d",&n,&m); ^ user.c:4:41: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("alee.in","r",stdin),freopen("alee.out","w",stdout),scanf("%d%d",&n,&m); ^ user.c:4:70: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("alee.in","r",stdin),freopen("alee.out","w",stdout),scanf("%d%d",&n,&m); ^ user.c:6:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&i,&k),a[i][k]=-1; ^ user.c:7:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d",&b,&d,&o,&q); ^