【洛谷P 1022】川を渡る卒

#include 
#include 
using namespace std;
#define LOCAL 1
/*
 1.         -1
 2.         0
 3.   0                
 4.                             
*/ 
//         0，        ，  long long 
long long m[21][21];

int main(){
    //      
#if LOCAL
    freopen ("datain.txt","r",stdin);
    freopen ("dataout.txt","w",stdout);
#endif
    //    8    
    int no[8][2] = { {1,2},{-1,2},{1,-2},{-1,-2},
                     {2,1},{-2,1},{2,-1},{-2,-1}
                   }; 
    //       ，            
    int bx,by,mx,my;
    cin >> bx >> by >> mx >> my; 
    //          -1 
    m[mx][my] = -1;
    for(int i = 0; i < 8; i++){
        int t1 = no[i][0] + mx;
        int t2 = no[i][1] + my;
        //             
        if(0 <= t1 && t1 <= bx && 0 <= t2 && t2 <= by){
            m[t1][t2] = -1;
        }
    }
    //         
    m[0][0] = 1;
    for(int i = 0; i <= bx; i++){
        for(int j = 0; j <= by; j++){
            //         ，    
            if(m[i][j] == -1){
                continue;
            }
            //              
            if(i - 1 >= 0 && m[i-1][j] != -1){
                m[i][j] +=  m[i-1][j];
            }
            //              
            if(j - 1 >= 0 && m[i][j-1] != -1){
                m[i][j] +=  m[i][j-1];
            }
        }
    }
//          
//  for(int i = 0; i <= bx; i++){
//      for(int j = 0; j <= by; j++){
//          cout << m[i][j] << "\t";
//      }
//      cout << endl;
//  }
    cout << m[bx][by] << endl;
    return 0;
}