#include <iostream>
using namespace std;
typedef long long ll;
ll n, 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);
}
int main()
{
	cin>>n>>k;
	cout<<solve(n)+1<<endl;
    return 0;
}