#include <stdio.h>
#include <string.h>
#include <math.h>
int main(void){
    long int a;
    char b[10];
    long int ans;
    int b_100;
    scanf("%ld%s", &a, b);
    b_100 = (b[0] - '0')*100 + (b[2] - '0')*10 + (b[3] - '0');
    //printf("%d\n", b_100);
    ans = a * b_100 / 100;
    printf("%ld\n", ans);

    return 0;
}
