'use strict'

function main(input) {

    x = +input

    let max = 1;
    let ans = 0

    for (let p = 2; p <= x; p++) {
        for (let i = 1; i <= x; i++) {

            ans = i ** 2
            if (ans <= x) max = Math.max(max, ans)

        }

    }
    console.log(max)
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));