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 Rust (1.15.1) (judge verdict: Wrong Answer)

// Vicfred
// https://atcoder.jp/contests/abc156/tasks/abc156_b
// simulation
use std::io;

fn main() {
    let mut line = String::new();

    io::stdin()
        .read_line(&mut line)
        .unwrap();

    let words: Vec<f64> =
        line
        .split_whitespace()
        .map(|x| x.parse().unwrap())
        .collect();

    let n = words[0];
    let k = words[1];

    let ans = f64::ceil(f64::log(n,10.0f64)*f64::log(10.0f64,k));

    println!("{}", ans as i64);
}