#include<bits/stdc++.h>
#define rep(i, x) for(ll i = 0; i < x; i++)
#define rep2(i, x) for(ll i = 1; i <= x; i++)
#define all(a) (a).begin(),(a).end()
using ll = long long;
using ld = long double;
using namespace std;

signed main() {
	string s; cin >> s;
	rep (i, s.size()) {
	    if (s[i] != (char)(i + 97)){
	        cout << s[i] << "to" << (char)(i + 97) << endl; return 0;
	    }
	}
	return 0;
}