#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
#define ll long long
int ctoi(const char c){
  if('0' <= c && c <= '9') return (c-'0');
  return -1;
}
int main()
{
    ll A;
    char B[5];
    scanf("%lld%s",&A,&B);
    printf("%lld",(A*(ctoi(B[0])*100+ctoi(B[2])*10+ctoi(B[3])))/100);
    return 0;
}