Problem:
Score : 200 points

Problem Statement

Given is an integer N. Find the number of digits that N has in base K.

Notes

For information on base-K representation, see Positional notation - Wikipedia.

Constraints

All values in input are integers.

1 \leq N \leq 10^9

2 \leq K \leq 10

Input

Input is given from Standard Input in the following format:

N K

Output

Print the number of digits that N has in base K.

Sample Input 1

11 2

Sample Output 1

4

In binary, 11 is represented as 1011.

Sample Input 2

1010101 10

Sample Output 2

7

Sample Input 3

314159265 3

Sample Output 3

18

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef long long int keytype;

//quicksort(<#keytype *a#>, <#int first#>, <#int last#>)

void quicksort(keytype a[], long long int first, long long int last){
    long long int i, j;
    keytype x, t;
    
    x = a[(first + last) / 2];
    i = first;  j = last;
    for ( ; ; ) {
        while (a[i] < x) i++;
        while (x < a[j]) j--;
        if (i >= j) break;
        t = a[i];  a[i] = a[j];  a[j] = t;
        i++;  j--;
    }
    if (first  < i - 1) quicksort(a, first , i - 1);
    if (j + 1 < last) quicksort(a, j + 1, last);
}

int main() {
    long long int n,k;
    long long int ans,count=0,i=0,j;
    scanf("%lld %lld",&n,&k);
    for(;;){
        ans=n%k;
        n=(n-ans)/k;
        
        if (ans<=k && k>=n) {
            break;
        }
        i++;
    }
    printf("%lld",i+2);
    return 0;
}