#include<stdio.h>
int main()
{
	int N,i1,i2,num=0;
	scanf("%d",&N);
	for(i1=3;i1<=N;i1++)
	{
		for(i2=2;i2<=i1;i2++)
		{
		if(i1%i2==0&&i1>i2)
		{num++;break;}
		}
	}
	printf("%d",N-(num+1));//加上2 
	return 0;
}

如何运行快一点，有八组2.2秒超时