#include <bits/stdc++.h>
#define _GLIBCXX_DEBUG 
#define rep(i, n) for (int i = 0; i < n; i++)
#define reps(i, s, n) for (int i = s; i < n; i++)
#define all(v) v.begin(), v.end() // sort(all(array))
#define INF 1000000000
#define mod 1000000007
using namespace std;
using ll = long long;
using vi = vector<int>; //vi array(要素数, 初期値)
using pll = pair<ll, ll>;
using pii = pair<int, int>;
using vc = vector<char>;
using vs = vector<string>;
using vb = vector<bool>;
using vvi = vector<vi>; //vvi table(行数, vi(列数, 初期値))
using vvc = vector<vc>;
using vvs = vector<vs>;
using vvb = vector<vb>;

int main() {
    int n, x, t; cin >> n >> x >> t;
    
    if(n % x == 0) {
        cout << (n / x) * t << endl;
    }
    else cout << t + (n / x) * t << endl;
}

#include <bits/stdc++.h>
using namespace std;
int main(){
 int N,K;
  cin >> N >> K;
  int X = 1;
   for(int i = 0; i < N; i++){
    if( X * 2 < X + K ){
     X = X * 2;
    }
    else{
     X = X + K;
    }
  }
  cout << X << endl;
}