import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;

/**
 * https://atcoder.jp/contests/abc169/tasks/abc169_c
 * Multiplication 3
 */
public class Main {
	public static void main(String...args) {
		try (Scanner sc= new Scanner(System.in)) {
			BigDecimal a = BigDecimal.valueOf(sc.nextLong());
			BigDecimal b = BigDecimal.valueOf(sc.nextDouble());
			BigInteger ans = a.multiply(b).toBigInteger();
			System.out.println(ans);
		}
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz