#include<bits/stdc++.h>
using namespace std;
int main()
{
    double n,m;cin>>n>>m;
    int y=n/10*m;
    int g=y%10;
    if(g>=5)
    {
        y=y+10-g;
    }
    else y-=g;
    cout<<y;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
double a;
double b;
int main(){
	cin>>a>>b;
	int t=a*b/10;
	int x=round(t);
	cout<<x;
	
	
	return 0;
}