#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>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#include <list>
#include <atcoder/all>
#define popcount __builtin_popcount
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef pair<int, int> P;
ll n, k;
ll solve(ll x){
	if(x<=k) return x-1;
	return solve(x-(x+k-1)/k)/(k-1)*k+1+solve(x-(x+k-1)/k)%(k-1);
}
int main()
{
	cin>>n>>k;
	cout<<solve(n)+1<<endl;
    return 0;
}