#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#define ll long long

ll a;
//double b;
char b[5];

int main(){
  scanf("%lld%s",&a,b);

  ll tmp=(b[0]-'0')*100+(b[2]-'0')*10+(b[3]-'0');
  //printf("%lld\n",tmp);
  ll ans=a*tmp/100;
  printf("%lld\n",ans);
  
  return 0;
}
