function Main(input) {
    const N = BigInt(input);
    let ok = 0n, ng = N;
    while (ng - ok > 1n) {
        const mid = (ok + ng) / 2n;
        mid ** 2n <= N ? ok = mid : ng = mid;
    }
    console.log(ok + "");
}
Main(require("fs").readFileSync(0)+"")