#include <iostream>
#include <stack>
#include <algorithm>
#include <fstream>

using namespace std;

void write(stack <char> s)
{
    stack <char> news = s;
    while (!news.empty())
    {
        cout << news.top() << " ";
        news.pop();
    }
    cout << endl;
}

int main() {
    //ifstream cin("input.txt");
    //ofstream cout("output.txt");

    string str1, str2;
    cin >> str1 >> str2;
    int length = str1.length();
    stack <char> s;
    int i1 = 0;

    for (int i = 0; i < length; i++) {
        write(s);
        char c = str2[i];
        if (c != str1[i1] && s.empty()) {
            while (c != str1[i1] && i1 < length) {
                s.push(str1[i1]);
                i1++;
            }
            if (i1 == length) {
                cout << "NO" ;
                return 0;
            }
        }
        else
        if (c != str1[i1] && !s.empty()) {
            if (c == s.top()) {
                s.pop();
            }
            else {
                cout << "NO" ;
                return 0;
            }
        }
        else
        if (c == str1[i1] && s.empty()) {
            i1++;
        }
        else
        if (c == str1[i1] && !s.empty()) {
            cout << "NO";
            return 0;
        }
    }

    cout << "YES" ;
}