#include<bits/stdc++.h>
using namespace std;

int main()
{
	int x,y,n;
	cin>>x>>y>>n;
	if((x-1)*10<(y-1)) cout<<(x-1)*n<<endl;
	else cout<<(n/10)*(y-1)+(n%10)*(x-1)<<endl;
	return 0;
}

评测记录：https://www.luogu.com.cn/record/178514243