#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
ll k;
ll solve(ll x){
    if(x<=k) return x;
    ll y=solve(x-(x+k-1)/k);
    ll q=y/(k-1), r=y%(k-1);
    if(r==0) return q*k;
    else return q*k+1+r;
}
int main()
{
    ll n; cin>>n>>k;
    cout<<solve(n)<<endl;
    return 0;
}