Compilare: user.c: In function ‘prod’: user.c:19:19: warning: unused variable ‘x’ [-Wunused-variable] int i,j=0,o=0,x; ^ user.c: At top level: user.c:34:5: warning: return type of ‘main’ is not ‘int’ [-Wmain] int main() ^ user.c: In function ‘main’: user.c:37:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("perm.in","r",stdin); ^ user.c:38:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("perm.out","w",stdout); ^ user.c:39:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%hd%hd",&n,&m); ^