#include<bits/stdc++.h>
using namespace std;
int main()
{
	double a,b;
	cin>>a>>b;
	int c=a*b/10;
	int d=c%10;
	int e=(c%100-d)/10;
	if(d<=4)
	{
		cout<<c-d;
	}
	else
	{
		cout<<c-d+10;
	}
	return 0; 
}