帮忙看看这个b，为什么过不了

#include<bits/stdc++.h>

using namespace std;

const int N = 510;

char a[N][N];

int main()

{

int n,m,k;

cin >> n>>m>>k;

for(int i = 1; i <= n;i++)

{

for(int j = 1; j <= m;j++)

a[i][j] = '.';

}

while(k--)

{

int x,y;

char c ;

cin >> x >>y >>c;

a[x][y] = c;

if(x+1<=m)a[x+1][y] = c;

if(x+2<=m)a[x+2][y] = c;

if(x-1>=1)a[x-1][y]=c;

if(x-2>=1)a[x-2][y]=c;

if(y+1<=n)a[x][y+1] = c;

if(y+2<=n)a[x][y+2] = c;

if(y-1>=1)a[x][y-1]=c;

if(y-2>=1)a[x][y-2]=c;

}

int j;

for(int i = 1; i <= n;i++)

{

for( j = 1; j <= m;j++){

cout << a[i][j];

if(j == m) cout << '\n';

}

}

}