问题标题: 酷町堂：5102

请问5102题我怎么错了：

#include<iostream>
#include<map> 
#include<bits/stdc++.h>
typedef unsigned long long ull;
using namespace std;
int n,cnt,m,x,y;
map<ull,map<ull,ull> >f,ma;
int main(){
    cin>>n>>m>>x>>y;
    ma[x+2][y+1]=1;
    ma[x+1][y+2]=1;
    ma[x-1][y+2]=1;
    ma[x-2][y+1]=1;
    ma[x+2][y-1]=1;
    ma[x+1][y-2]=1;
    ma[x-1][y-2]=1;
    ma[x-2][y-1]=1;
    f[0][0]=1;
    for(int i=0;i<=n;i++){
        for(int j=0;j<=m;j++){
            if(i==x||j==y||ma[i][j]) continue;
            if(i==0&&j==0) continue;
            int sum=0;
            for(int k=0;k<=i;k++){
                sum+=f[k][j];
            }
            for(int k=0;k<=j;k++){
                sum+=f[i][k];
            } 
            f[i][j]=sum;
//          cout<<sum<<' ';
        }
//      cout<<endl;
    }
    cout<<f[n][m];
}