#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;


int main() {
    string A = "abcdefghijklmnopqrstuvwxyz";
    string S;
    cin >> S;

    for (int i = 0; i < A.size(); ++i) {
        if (A[i] != S[i]) {
            cout << A[i] << "to" << S[i] << endl;
            break;
        }
    }

    return 0;

}