#include<bits/stdc++.h>
using namespace std;
int main(){
	unsigned int n,m;
	cin>>n>>m;
	int a,b,x;
	cin>>a>>b>>x;
	unsigned long long ans=n*m;
	long long y,z,yy,zz;
	if(n%2==1){
		if(m%2==1)y=(n/2+1)*(m/2+1);
		else y=(n/2+1)*(m/2);
		z=(n/2+1)*(m/2);
	}
	else{
		if(m%2==1)y=(n/2)*(m/2+1);
		else y=(n/2)*(m/2);
		z=(n/2)*(m/2);	
	}
	if(m%2==1)yy=(n/2)*(m/2+1);
	else yy=(n/2)*(m/2);
	zz=(n/2)*(m/2);
	if(x==1){
		if(a%2==1&&b%2==1){
			ans-=z;
		}
		else ans-=y;
	}
	else{
	    if(a%2==0){
			if(b%2==0)ans-=zz;
			else ans-=yy;
		}
		else{
		    if(b%2==0)ans-=z;
		    else ans-=y;
		}
		
    }
	cout<<ans<<endl;
	return 0;
}