编译失败？

#include<bits/stdc++.h>
using namespace std;
#define f(i,t,n) for(register int i=t;i<=n;++i)
int a[15][15],d[15][15][15][15];
signed main(){
	int n;cin>>n;
	while(1){
		int x,y,z;cin>>x>>y>>z;
		if(x&&y&&z)a[x][y]=z;
		else break;
	}
	f(i,1,n){
		f(j,1,n){
			f(x,1,n){
				f(y,1,n){
					d[i][j][x][y]=max(d[i-1][j][x-1][y],max(d[i][j-1][x-1][y],max(d[i][j-1][x][y-1],d[i-1][j][x][y-1])))+a[i][j]+a[x][y];
					if(i==x&&j==y) d[i][j][x][y]-=a[i][j];
				}
			}
		}
	}
	cout<<d[n][n][n][n];
	return 0;
}