判断素数

#include <stdio.h>#include <iostream>#include <math.h>using namespace std;int main(){int n;scanf("%d",&n);int flag=1;for(int i=2;i<=sqrt(n);i++){if(n%i==0){flag=0;}}if(flag)printf("This is a prime.\n");elseprintf("This is not a prime.\n");return 0;}