13706.java

// 13706. 제곱근
// 2019.12.02
// 수학
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;

public class test {
	public static BigInteger sqrt(BigInteger x) {
		BigInteger div = BigInteger.ZERO.setBit(x.bitLength() / 2);
		BigInteger div2 = div;
		for (;;) {
			BigInteger y = div.add(x.divide(div)).shiftRight(1);
			if (y.equals(div) || y.equals(div2))
				return y;
			div2 = div;
			div = y;
		}
	}

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BigInteger n = new BigInteger(br.readLine());

		System.out.println(sqrt(n));

	}
}