#include <bits/stdc++.h>
using namespace std;
using lint = long long;
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V< V<T> >;

int main() {
  cin.tie(nullptr); ios::sync_with_stdio(false);
  int q; cin >> q;
  while (q--) {
    lint n, k; cin >> n >> k;
    if (k == 1) {
      cout << n - 1 << '\n';
    } else {
      auto chk = [&](lint d) -> bool {
        lint s = 1, t = 1;
        for (int i = 0; i < d; ++i) {
          t *= k;
          s += t;
          if (s >= n) break;
        }
        return n <= s;
      };
      lint ng = -1, ok = n;
      while (ok - ng > 1) {
        lint mid = ng + ok >> 1;
        (chk(mid) ? ok : ng) = mid;
      }
      cout << ok << '\n';
    }
  }
}