#include "testlib.h"
#include <iostream>
using namespace std;
typedef long long ll;
ll n;
int k;
ll solve(ll x){
	if(x<=k) return x-1;
	ll y=solve(x-(x+k-1)/k);
	return y/(k-1)*k+1+y%(k-1);
}
const ll MAXN=1000000000000000000ll;
const int MAXK=10000;
int main(int argc, char* argv[]){
    registerValidation(argc, argv);
    n=inf.readLong(1ll, MAXN);
    inf.readSpace();
    k=inf.readInt(2, MAXK);
    inf.readEoln();
    inf.readEof();
	cout<<solve(n)+1<<endl;
    return 0;
}