#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

int main() {
    string s, t = "abcdefghijklmnopqrstuvwxyz";
    cin >> s;

    rep(i, s.size()) {
        if (s[i] != t[i]) {
            cout << t[i] << "to" << s[i] << endl;
            break;
        }
    }

    return 0;
}