P1002巨佬求调！debug了一下没啥问题，不知道为啥只能40分？

#include <iostream>
#include <cmath>
using namespace std;

const int ERR = -1;
int a[2000][2000];
int main()
{
    int x, y, ma_x, ma_y;
    cin >> x >> y >> ma_x >> ma_y;

    for (int i = 0; i <= x; i++)
    {
        for (int j = 0; j <= y; j++)
        {
            if (i == 0) a[i][j] = 1;
            else if (j == 0) a[i][j] = 1;
            else if (i == ma_x && j == ma_y) a[i][j] = 0;
            else if (abs(i - ma_x) == 2 && abs(j - ma_y) == 1) a[i][j] = 0;
            else if (abs(i - ma_x) == 1 && abs(j - ma_y) == 2) a[i][j] = 0;
            else a[i][j] = ERR;
        }
    }
    for (int i = 1; i <= x; i++)
    {
        for (int j = 1; j <= y; j++)
        {
            if (a[i][j] == ERR) a[i][j] = a[i - 1][j] + a[i][j - 1];
            // cout << i << j << ": " << a[i][j] << " ";
        }
   	// cout << endl;
    }
    cout << a[x][y];
}