#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define REP(i, n) FOR(i,0,n)

int main()
{
    lint Q, N, K;
    cin >> Q;
    REP(_, Q)
    {
        cin >> N >> K;
        lint ret = 0, a = 1;
        while (a < N) ret++, a = a * K + 1;
        cout << ret << endl;
    }
}