#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; 
}

#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;
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;
}