求调

#include<bits/stdc++.h>
using namespace std;

int a,b,all;

int main(){
	
	cin>>a>>b;
	
	bool flag;
	
	for(int i=a;i<=b;i++){
		for(int j=2;j*j<=i;j++){
		
			if(i%j==0) flag=!flag;
			
	}
		
		if(flag) all++;
		
	}
	
	cout<<all;
	
	
	return 0;
}