#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

int main()
{
    string a, b;
    cin >> a >> b;

    for(int i=0; i<a.length(); i++){
        if(b[i] < a[i]){
            cout << "YES" << endl;
            return 0;
        }
        else if(b[i] > a[i]) {
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;

    return 0;
}