#include<bits/stdc++.h>
using namespace std;

int main()
{
    int m,n,count=0,i,j,k,t;
    cin>>t;
    while(t--)
    {
        count=0;
        cin>>n>>m;
        while(n>=m)
        {
            n=n-m+1;
            count++;
        }
        if(n==1)
            cout<<count<<endl;
        else
            cout<<"cannot do this"<<endl;
    }
    return 0;
}