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

int main() {
    string S;
    cin >> S;
    for (int i = 0; i < 26; i++) {
        int t = S[i] - 'a';
        if (t != i) {
            cout << (char)('a' + i) << "to" << S[i] << endl;
            return 0;
        }
    }

    return 0;
}