const { createInterface: ci } = require('readline')

const input = await new Promise(res => ci(process.stdin, process.stdout).once('line', res));
const list = 'abcdefghijklmnopqrstuvwxyz'
const i = list.split('').findIndex((c, i) => c !== input[i])

console.log(`${list[i]}to${input[i]}`)