Compilare: user.c: In function ‘main’: user.c:24:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("sir4.in","r",stdin),freopen("sir4.out","w",stdout),scanf("%llu%llu%llu%llu%llu\n",&y,&a,&b,&m,&q); ^ user.c:24:38: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("sir4.in","r",stdin),freopen("sir4.out","w",stdout),scanf("%llu%llu%llu%llu%llu\n",&y,&a,&b,&m,&q); ^ user.c:24:67: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("sir4.in","r",stdin),freopen("sir4.out","w",stdout),scanf("%llu%llu%llu%llu%llu\n",&y,&a,&b,&m,&q); ^ user.c:31:7: warning: ignoring return value of ‘gets’, declared with attribute warn_unused_result [-Wunused-result] gets(s),u[0]=strlen(s)-1; ^ /tmp/ccJeEe2c.o: In function `main': user.c:(.text.startup+0x233): warning: the `gets' function is dangerous and should not be used.