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

int a,b,c;
int s;
int g;

signed main(){
	
	cin>>a>>b>>c;
	if(a%c==0&&b%c==0){
		s=c*c;
		cout<<(a*b)/s<<endl;
		return 0;
	}
	cout<<-1<<endl;
	return 0;
}