Square Matrix I

#include<stdio.h>
int main()
{
    int i,j,n,z,l,a,b;
    while(1)
    {
        scanf("%d",&n);
        if(n==0)
            break;

        int arr[n][n];

        z=n/2;
        if(n%2==1)
            z++;
        a=0;
        b=n-1;
        for(l=1; l<=z; l++)
        {
            for(i=a; i<=b; i++)
            {
                for(j=a; j<=b; j++)
                {
                    arr[i][j]=l;
                }
            }
            a++;
            b--;
        }

        for(i=0; i<n; i++)
        {
            for(j=0; j<n; j++)
            {
                if(j==0)
                {
                    printf("%3d",arr[i][j]);
                }
                else
                    printf(" %3d",arr[i][j]);
            }
            printf("\n");
        }
        printf("\n");
    }

    return 0;
}