过河卒问题：简单动规

#include 
#include 
#include 
#include 
using namespace std;
const int hmx[8]={-2,-1,1,2,2,1,-1,-2};
const int hmy[8]={1,2,2,1,-1,-2,-2,-1};
int hx,hy;
int check(long long int x,long long int y)
{
    int i;
    for(i=0;i<8;i++) if(hx+hmx[i]==x&&hy+hmy[i]==y) break;
    if(i==8&&(x!=hx||y!=hy))return 0;
    else return 1;
}
int main()
{
    long long int i,j,ex,ey,a[25][25];
    cin>>ex>>ey>>hx>>hy;
    memset(a,0,sizeof(a));
    a[0][0]=1;
    for(i=0;i<=ey;i++)
    {
        for(j=0;j<=ex;j++)
        {
            if(i+j==0)continue;
            if(check(j,i))continue;
            if(i>0) a[i][j]+=a[i-1][j];
            if(j>0) a[i][j]+=a[i][j-1];
        }
    }
    cout<