#include<stdio.h>
int main()
{
    unsigned long long int a,d,e;
    float b,c;
    scanf("%llu",&a);
    scanf("%f",&b);
    b=b*100;
    e=(int)b;
    c=(a*b)/100;
    d=(unsigned long long int)c;
    printf("%llu",d);
    return 0;
}