#include <iostream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvv vector<vvl>
#define vvi vector<vector<int> >
#define vvl vector<vector<ll> >
#define vv(a, b, c, d) vector<vector<d> >(a, vector<d>(b, c))
#define vvvl(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define rep(c, a, b) for(ll c=a;c<b;c++)
#define re(c, b) for(ll c=0;c<b;c++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

ll mpow(ll a, ll b, ll p = -1){
  ll ret = 1, num = a;
  if(p==-1){
    while(b>0){
      if(b%2) ret *= num;
      num = num * num;
      b /= 2;
    }
  }else{
    while(b>0){
      if(b%2) ret = (ret*num)%p;
      num = (num*num)%p;
      b /= 2;
    }
  }
  return ret;
}
int main(int argc, char const *argv[]) {
  ll q;std::cin >> q;
  re(Q, q){
    ll n, k;std::cin >> n >> k;
    if(k==1) std::cout << n-1 << '\n';
    else{
      ll z = 1;
      while(true){
        ll tmp = mpow(k, z);
        tmp--;tmp/=k-1;
        if(tmp>=n) {
          std::cout << z - 1 << '\n';
          break;
        }
        z++;
      }
    }
  }

  return 0;
}