rt，本蒟蒻开1e8的数组时就会全MLE，开1e7时最后两个点就会过不了

#include<iostream>
#include<iostream>
#include<cstring>

using namespace std;
const int MAX=1e7+1;
int a[MAX],prime[MAX];
int main(){
	int n,m=0;
	cin>>n;
	memset(a,0,sizeof(a)); 
	for(int i=2;i<=n;i++){
		if(a[i]==0){
			a[i]=i;
			prime[++m]=i;
		}
		for(int j=1;j<=m;j++){
			if(prime[j]>a[i]||prime[j]>n/i)break;
			a[i*prime[j]]=prime[j];
		}
	}
	cout<<m; 
}