View Code of Problem 103

#include<iostream>
#include<algorithm>
#include<cmath>
#include<vector>
using namespace std;
vector<int> prime;
const int MAX=1000001;
bool h[MAX]={0};
void f(){
	for(int i=2;i<MAX;i++){
		if(h[i]==false)	{
			prime.push_back(i);
			for(int j=i+i;j<MAX;j+=i){
				h[j]=true;
			}
		}	
	}
}
int main(){
	long long a,b;
	f();
	h[1]=true;
	while((scanf("%d %d",&a,&b))!=EOF){
		vector<int>::iterator s1= lower_bound(prime.begin(),prime.end(), a);
        vector<int>::iterator s2= upper_bound(prime.begin(),prime.end(), b); 
		printf("%d\n",distance(s1,s2));
	}
}