#include<iostream>
using namespace std;
int main(){
	int tx, ty, mx, my;
	long long f[25][25]={0};
	cin>>tx>>ty>>mx>>my;
    tx+=1;ty+=1;mx+=1;my+=1;
    f[1][0] = 1;
    for(int i = 1; i <= tx; i++){
        for(int j =1; j <= ty; j++){
            if((i-mx)*(i-mx)+(j-my)*(j-my)==5||(i==mx&&j==my)) continue;
            f[i][j] = f[i - 1][j] + f[i][j - 1];
        }
    }
    cout<<f[tx][ty];
    return 0;
}