#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
const int fx[9] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
const int fy[9] = {0, 1, 2, 2, 1, -1, -2, -2, -1};
int bx, by, mx, my;
long long f[40][40];
bool s[40][40];
int main()
{
    scanf("%d%d%d%d",&bx,&by,&mx,&my);
    bx=bx+2; 
    by=by+2; 
    mx=mx+2;
    my=my+2;
    f[2][1]=1;
    s[mx][my]=1;
    for(int i=1;i<=8;i=i+1)s[mx+fx[i]][my+fy[i]]=1;
    for(int i=2;i<=bx;i=i+1)
    {
        for(int j=2;j<=by;j=j+1)
        {
            if(s[i][j]) continue;
            f[i][j]=f[i-1][j]+f[i][j-1];
        }
    }
    printf("%lld\n", f[bx][by]);
    return 0;
}