递归代码

#include<iostream>
#include<cstdio>
using namespace std;
int n,m,x,y,sum=1;
void dfs(int a,int b)
{
    if(a==n&&b==m)
    {
        return; 
    }
    if(a>n||b>m)
    {    
        sum--;
        return;
    }
    if((a==x&&b==y)||(a==x-1&&b==y-2)||(a==x-2&&b==y-1)||(a==x-2&&b==y+1)||(a==x-1&&b==y+2)||(a==x+1&&b==y+2)||(a==x+2&&b==y+1)||(a==x+2&&b==y-1)||(a==x+1&&b==y-2))
    {
        sum--;
        return;
    }
    sum++;
    dfs(a+1,b);
    dfs(a,b+1);
}
int main()
{
    scanf("%d%d%d%d",&n,&m,&x,&y);
    dfs(0,0);
    printf("%d\n",sum);
    return 0;
}