#include <stdio.h>
#include <string.h>

int main(void) {
  long long A;
  char B[4];
  scanf("%lld%s", &A, B);
  long long C = (B[0]-'0')*100+(B[2]-'0')*10+(B[3]-'0');
  long long ans = A * C;
  ans /= 100;
  printf("%lld\n",ans);
  return 0;
}
