import java.util.*;

class Main {
    public static void main(String[] args) {
        new Solver().run();
    }
}

class Solver {

    public void run() {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        String[] B = sc.next().split("\\.");

        int b1 = Integer.parseInt(B[0]);
        int b2 = Integer.parseInt(B[1]);
        //System.out.println(b1);
        //System.out.println(b2);

        int b = b1 * 100 + b2;
        long ans = A * b;
        System.out.println(ans/100);
        return;
    }

}
/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