Compilare: main.c: In function 'main': main.c:6:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("cal.in","r",stdin),freopen("cal.out","w",stdout),scanf("%d%d%d%d",&a,&b,&s,&n); ^~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:6:33: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("cal.in","r",stdin),freopen("cal.out","w",stdout),scanf("%d%d%d%d",&a,&b,&s,&n); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:6:63: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] freopen("cal.in","r",stdin),freopen("cal.out","w",stdout),scanf("%d%d%d%d",&a,&b,&s,&n); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:8:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&c,&d); ^~~~~~~~~~~~~~~~~~~