#include<stdio.h>
 
int main(){
  
 unsigned long long int a,d,ans;
 double b,c;
 
  (void) scanf("%llu %lf",&a,&b);
  
  c=b*1000;
  
  d=c/10;
  //printf("%lf %lln %lf\n",b,d,b);
    ans=a*d;
   //printf("%llu %llu %llu\n",a,d,a*c);
  
 printf("%llu",ans/100);
  
 return 0; 
}