#include <bits/stdc++.h>

using ll = long long;

using namespace std;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string s;
    cin >> s;

    const string s0 = "abcdefghijklmnopqrstuvwxyz";
    for (int i=0;i<26;++i)
    {
        if (s0[i] != s[i])
        {
            cout << s0[i] << "to" << s[i] << "\n";
            break;
        }
    }

    return 0;
}