#include <bits/stdc++.h>

using namespace std;

using ll =  long long;
using Pll = pair<ll, ll>;
using Pii = pair<int, int>;

constexpr ll MOD = 1000000007;
constexpr long double EPS = 1e-10;
constexpr int dyx[4][2] = {
    { 0, 1}, {-1, 0}, {0,-1}, {1, 0}
};

ll solve(ll n, ll k) {
    if(k == 1) return n-1;
    if(n == 1) return 0;
    ll ng = 0, ok = n;
    while(ok - ng > 1LL) {
        ll mid = (ok + ng) / 2;
        if((pow(k, mid) - 1) / (k-1) >= n) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    return ok-1;
}

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    int Q;
    cin >> Q;
    ll n, k;
    while(Q--) {
        cin >> n >> k;
        cout << solve(n, k) << endl;
    }
}