int main()
{
 int n, m;
 scanf("%d", &n);
 for(m=2;m<=n-1;m++)
 {
  if(n%m == 0)
  {
   printf("The number is not a prime number");
   return 0;
  }
 }
 printf("The number is a prime number");
 return 1;
}


为什么不能用else，两个return是什么意思