#include<bits/stdc++.h>
using namespace std;
bool p(int y){
	return y&400==0||y&100!=0&&y&4==0;
}
long long w[3001],m,n,s=0;
int main(){
	for(int i=1901;i<=3000;i++){
		if(p[i])	w[i]=(w[i-1]+1)%7;
		else	w[i]=(w[i-1])%7; 
	}
	cin>>m>>n;
	for(int i=m;i<=n;i++){
		if(w[i]==6||w[i]==0)	s++;
	}
	cout<<s<<endl;
	return 0;
}