const { createInterface } = require('readline')

const main = async () => {
    const input = await new Promise(res => createInterface(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]}`)
}
main()