#include <iostream>
#include <string>
using namespace std;
string s,t;
int main(){
    cin>>s>>t;
    for(int i=0;i<5;i++){
        if(s[i]<t[i]){
            cout<<"NO\n";
            return 0;
        }if(s[i]>t[i]){
            cout<<"YES\n";
            return 0;
        }
    }
    cout<<"Yes\n";
    return 0;
}