View Code of Problem 103

#include<iostream>
#include<bits/stdc++.h>
#include<string.h>
#include<cstring>
#include<string>
#include<sstream>
using namespace std;
int a[1000000];
bool issu(int a) {
	if(a==2||a==3)
		return true;
	else {
		for(int i=2; i<=sqrt(a); i++) {
			if(a%i==0)
				return false;
		}
		return true;
	}

}
int main() {
	int n1,n2;
	memset(a,0,sizeof(a));
	for(int i=1;i<1000000;i++)
		{
			if(issu(i))
			a[i]=a[i-1]+1;
			else
			a[i]=a[i-1];
		}
	while(cin>>n1>>n2)
	{

		cout<<a[n2]-a[n1-1]<<endl;
	}
	
	return 0;

}