#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
//-------------------------------------------------------

int X1,X2,Y1,Y2,D;

ll hoge2(ll x,ll y,ll D) {
	if(D<=y) {
		y=D;
		x=min(x,D);
		return (y+1+(y+1-x))*(x+1)/2;
	}
	else {
		ll ret=0;
		ll nx=D-y;
		return nx*(y+1) + hoge2(x-nx,y,y);
	}
	
}


ll hoge(ll x1,ll x2,ll y1,ll y2,ll D) {
	if(x1+y1>D) return 0;
	if(x2+y2<=D) return (y2-y1+1)*(x2-x1+1);
	return hoge2(x2-x1,y2-y1,D-(x1+y1));
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>X1>>Y1>>X2>>Y2>>D;
	cout<<hoge2(X1,Y1,D)<<endl;
	return;
	
	ll ret=0;
	if(X2<0) X1=-X1,X2=-X2,swap(X1,X2);
	if(Y2<0) Y1=-Y1,Y2=-Y2,swap(Y1,Y2);
	
	ret += hoge(max(0,X1),X2,max(0,Y1),Y2,D);
	if(X1<0) ret += hoge(0,-X1,max(0,Y1),Y2,D);
	if(Y1<0) ret += hoge(max(0,X1),X2,0,-Y1,D);
	if(X1<0 && Y1<0) ret += hoge(0,-X1,0,-Y1,D);
	
	if(X1<0) ret -= Y2-Y1+1;
	if(Y1<0) ret -= X2-X1+1;
	if(X1<0&& Y1<0) ret++;
	cout<<ret<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false);
	FOR(i,argc-1) s+=argv[i+1],s+='\n';
	FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	solve(); return 0;
}