Find nth number with digits 0,1,2,3,4,5

#include<stdio.h>
int fun(int a[], int n, int base)
{
int i =0,j, r;
if (n==0)
return 0;
while (n > 0)
          {
r = n % base;
a[i++] = r;
n /= base;
}
return i;
}

int main() {
    int n,rem,arr[100],i=0;
    scanf("%d",&n);
   int x = fun(arr, n - 1, 6);
   for (int i = x - 1; i >= 0; i--)
   printf("%d",arr[i]);
    
}