using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var a = ReadLine().ToList();
        var b = ReadLine().ToList();
        if (a.Count < b.Count) a = Enumerable.Repeat('0', b.Count - a.Count).Concat(a).ToList();
        if (a.Count > b.Count) b = Enumerable.Repeat('0', a.Count - b.Count).Concat(b).ToList();
        var ans = 0;
        for (var i = 0; i < a.Count; ++i)
        {
            ans = ans * 2 + (a[i] - '0') ^ (b[i] - '0');
        }
        WriteLine(ans);
    }
}