#include<bits/stdc++.h>

using namespace std;

int main() {

	long long x,y,n,ans;
	cin>>x>>y>>n;
	int ny,nx;
		if(n>=10){
			ny=n/10;
			nx=n%10;
			ans=ny*(y-1)+nx*(x-1);
		}else{
			ans=(x-1)*n;
		}
	cout<<ans;
	return 0;
}