#![allow(unused)]

use kyoproio::*;
use std::{
    collections::*,
    io::{self, prelude::*},
    iter,
    mem::{replace, swap},
};

fn main() -> io::Result<()> {
    std::thread::Builder::new()
        .stack_size(50 * 1024 * 1024)
        .spawn(solve)?
        .join()
        .unwrap();
    Ok(())
}

fn solve() {
    let stdin = io::stdin();
    let mut kin = Input::new(stdin.lock());
    let stdout = io::stdout();
    let mut out = io::BufWriter::new(stdout.lock());
    macro_rules! output {
        ($($args:expr),+) => { write!(&mut out, $($args),+) };
    }
    macro_rules! outputln {
        ($($args:expr),+) => { output!($($args),+); outputln!() };
        () => { output!("\n"); if cfg!(debug_assertions) { out.flush(); } }
    }

    let t: u32 = kin.input();
    for _ in 0..t {
        let (mut n, k): (i64, i64) = kin.input();
        let depth = if k > 1 {
            let mut depth = -1;
            let mut x = 1;
            while n > 0 {
                n -= x;
                x *= k;
                depth += 1;
            }
            depth
        } else {
            n - 1
        };
        outputln!("{}", depth);
    }
}

// -----------------------------------------------------------------------------
pub mod kyoproio {
    #![warn(unused)]

    pub use std::io::prelude::*;

    pub struct Input<R> {
        src: R,
        buf: String,
        pos: usize,
    }
    impl<R: BufRead> Input<R> {
        pub fn new(src: R) -> Self {
            Self {
                src,
                buf: String::with_capacity(1024),
                pos: 0,
            }
        }
        pub fn str(&mut self) -> &str {
            loop {
                if self.pos >= self.buf.len() {
                    self.buf.clear();
                    let len = self.src.read_line(&mut self.buf).expect("io error");
                    self.pos = 0;
                    if len == 0 {
                        return &self.buf;
                    }
                }
                let range = self.pos
                    ..self.buf[self.pos..]
                        .find(|c: char| c.is_ascii_whitespace())
                        .map(|i| i + self.pos)
                        .unwrap_or(self.buf.len());
                self.pos = range.end + 1;
                if range.end - range.start > 0 {
                    return &self.buf[range];
                }
            }
        }
        pub fn bytes(&mut self) -> &[u8] {
            self.str().as_ref()
        }
        pub fn input<T: InputParse>(&mut self) -> T {
            self.input_fallible().expect("input error")
        }
        pub fn input_fallible<T: InputParse>(&mut self) -> Result<T> {
            T::input(self)
        }
        pub fn iter<T: InputParse>(&mut self) -> Iter<T, R> {
            Iter {
                input: self,
                _t: std::marker::PhantomData,
            }
        }
    }
    pub struct Iter<'a, T, R> {
        input: &'a mut Input<R>,
        _t: std::marker::PhantomData<T>,
    }
    impl<'a, T: InputParse, R: BufRead> Iterator for Iter<'a, T, R> {
        type Item = T;
        fn next(&mut self) -> Option<Self::Item> {
            Some(self.input.input())
        }
    }
    type Result<T> = std::result::Result<T, Box<dyn std::error::Error + 'static>>;
    pub trait InputParse: Sized {
        fn input<R: BufRead>(input: &mut Input<R>) -> Result<Self>;
    }
    macro_rules! input_from_str_impls {
        { $($T:ty)* } => {
            $(impl InputParse for $T {
                fn input<R: BufRead>(input: &mut Input<R>) -> Result<Self> {
                    input.str().parse::<$T>().map_err(|e| e.into())
                }
            })*
        };
    }
    macro_rules! input_tuple_impls {
        { $(($($T:ident),+))* } => {
            $(impl<$($T:InputParse),+> InputParse for ($($T),+) {
                fn input<R: BufRead>(input: &mut Input<R>) -> Result<Self> {
                    Ok(($($T::input(input)?),+))
                }
            })*
        };
    }
    input_from_str_impls! {
        String char bool f32 f64
        isize i8 i16 i32 i64 i128
        usize u8 u16 u32 u64 u128
    }
    input_tuple_impls! {
        (A, B)
        (A, B, C)
        (A, B, C, D)
        (A, B, C, D, E)
        (A, B, C, D, E, F)
        (A, B, C, D, E, F, G)
    }
}