如下程序报如下错误，如何解决？急！

#include<iostream>
#include<cstdio>
#include<cmath>
#include<vector>
#define MAXN 1000
#define cfor(i,a,b) for(int i=(a);i<(b);i++)

using namespace std;
int main(){
	int n;
	
	
	cin>>n;
	
	vector< vector<int> >ans(n,0);
	cfor(i,0,n)ans[i].resize(n,0);
	
	int m=pow(n,2);
	for(int i=0,j=0,k=1;k<=m;){
		while(i<n&&j<n&&k<=m&&ans[i][j]==0){
			ans[i][j]=k;
			i++;
			k++;
		}
		i--;
		while(i<n&&j<n&&k<=m&&ans[i][j]==0){
			ans[i][j]=k;
			j++;
			k++;
		}
		j--;
		while(i<n&&j<n&&k<=m&&ans[i][j]==0){
			ans[i][j]=k;
			i--;
			k++;
		}
			while(i<n&&j<n&&k<=m&&ans[i][j]==0){
			ans[i][j]=k;
			j--;
			k++;
		}
			
	}
	cfor(i,0,n){
		cfor(j,0,n){
			printf("%3d",ans[i][j]);
		}
		printf("\n");
	}

	//cout<<a[ans]<<endl;

	


	

	return 0;
}