Compilare: main.c: In function 'main': main.c:20:2: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("costperm.in","r",stdin),freopen("costperm.out","w",stdout),scanf("%d",&n); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:20:35: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("costperm.in","r",stdin),freopen("costperm.out","w",stdout),scanf("%d",&n); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:20:70: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] freopen("costperm.in","r",stdin),freopen("costperm.out","w",stdout),scanf("%d",&n); ^~~~~~~~~~~~~~ main.c:22:7: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",a+i); ^~~~~~~~~~~~~~~