Compilare: user.c: In function ‘main’: user.c:18:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("dusman.in","r",stdin),freopen("dusman.out","w",stdout),scanf("%d%d%d",&n,&k,&m); ^ user.c:18:43: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("dusman.in","r",stdin),freopen("dusman.out","w",stdout),scanf("%d%d%d",&n,&k,&m); ^ user.c:18:74: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("dusman.in","r",stdin),freopen("dusman.out","w",stdout),scanf("%d%d%d",&n,&k,&m); ^ user.c:20:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&i,&j),a[i][j]=a[j][i]=1; ^