1 #include<cstdio>
 2 #include<cmath>
 3 #include<queue>
 4 #include<cstring>
 5 #include<stdlib.h>
 6 #include<algorithm>
 7 using namespace std;
 8 const int MAXN=1000+10;
 9 const int INF=-0x3f3f3f3f;
10 struct node
11 {
12     int x,y;
13     int step;
14 }p;
15 int starx,stary,ans;
16 int n,m,x,y,ok;
17 int vis[MAXN][MAXN];
18 int dir[4][2]={{0,1},{1,0},{0,-1},{-1,0}};
19 void BFS()
20 {
21     memset(vis,0,sizeof(vis));
22     queue<node> Q;
23     ans=0;
24     p.x=starx;
25     p.y=stary;
26     p.step=0;
27     Q.push(p);
28     while(!Q.empty())
29     {
30         node now,next;
31         now=Q.front();
32         Q.pop();
33         for(int i=0;i<4;i++)
34         {
35             next.x=now.x+dir[i][0];
36             next.y=now.y+dir[i][1];
37             next.step=now.step+1;
38             if(0<=next.x && next.x<n && 0<=next.y && next.y<m && !vis[next.x][next.y] && next.step<=ok)
39             {
40                 vis[next.x][next.y]=1;
41                 ans++;
42                 Q.push(next);
43             }
44         }
45     }
46 }
47 int main()
48 {
49     //freopen("in.txt","r",stdin);
50     scanf("%d %d %d %d %d",&n,&m,&x,&y,&ok);
51     starx=x-1;
52     stary=y-1;
53     BFS();
54     printf("%d\n",ans);
55     return 0;
56 }