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

public class Main {
    private static final int MOD = 1_000_000_007;
    private static final String YES = "Yes";
    private static final String NO = "No";

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long A = sc.nextLong();
        double B = sc.nextDouble();

        System.out.println(solve(A, B));
    }

    private static String solve(long A, double B) {
        BigDecimal b = BigDecimal.valueOf(A);
        b = b.multiply(BigDecimal.valueOf(B));


        return b.setScale(0, RoundingMode.DOWN).toString();
    }
}
/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