为什么a[n][n]过不了,a[n+5][n+5]能过

#include<stdio.h>
int main()
{
    int i,j,h,n,m,k,x,y,o,p,cnt=0;
    scanf("%d %d %d",&n,&m,&k); 
	int c[n][n];  //定义变量
    for ( i=0; i<n; i++ ) {
    	 for ( j=0; j<n; j++ ) {
            c[i][j]=0;//数组调0
		 }
    }
    for ( h=2; h<=m+1; h++ ) {
        scanf("%d %d",&x,&y);
        for ( i=x-2; i<=x; ++i ) {
        	for ( j=y-2; j<=y; ++j ) {
        		c[i][j]=1;
			}
		}
        c[x-3][y-1]=1;
        c[x+1][y-1]=1;
        c[x-1][y-3]=1;
        c[x-1][y+1]=1;//火把有光调1
    }
    for ( h=m+2; h<=m+k+1; h++ ) {
    	scanf("%d %d",&o,&p);
    	for ( i=o-3; i<=o+1; i++ ) {
        	for ( j=p-3; j<=p+1; j++ ) {
        		c[i][j]=1;//萤火石有光调1
			}
		}
	}
    for ( i=0; i<n; ++i ) {
    	 for ( j=0; j<n; ++j ) {
            if ( c[i][j]==0 ) {
            	cnt++;//cnt计数
			}
		 }
    }
    printf("%d",cnt);//输出
    return 0;
}