c39III

#include <iostream>
#include <string>
using namespace std;

char a;
char b;

void solve(string & s, int pos)
{
    if (s[pos] == a)
    {
        string t1 = s.substr(0, pos + 1);
        string t2 = s.substr(pos + 1, s.length() - pos + 1);
        s = t1 + b + t2;
        pos++;
    }

    if (pos + 1 != s.length())
        solve(s, pos + 1);

}
int main()
{
    cin >> a >> b;
    string s;
    cin >> s;
    solve(s, 0);
    cout << s;
}