#include <bits/stdc++.h>

#define cn count
#define pb push_back
#define in insert
#define fs first
#define sc second
#define sz size
#define len length
#define forn(i, n) for (ll i = 0; i < (ll) (n); ++i)
#define forni(i, n) for (ll i = 1; i < (ll) (n); ++i)
#define IO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)

using namespace std;
using ll = long long;
const ll inf = 1e9+7; 
const double PI =  3.141592653589793;

int main(){
	IO;
	ll n,x,t;
	cin>>n>>x>>t;
	cout<<((n+x-1)/x)*t<<'\n';
	return 0;
}


// _   .-')                .-. .-')                 .-')                                               
//( '.( OO )_              \  ( OO )               ( OO ).                                             
// ,--.   ,--.).-'),-----. ,--. ,--.  .-'),-----. (_)---\_) ,--. ,--.     .-----.  ,-.-')  .-'),-----. 
// |   `.'   |( OO'  .-.  '|  .'   / ( OO'  .-.  '/    _ |  |  | |  |    '  .--./  |  |OO)( OO'  .-.  '
// |         |/   |  | |  ||      /, /   |  | |  |\  :` `.  |  | | .-')  |  |('-.  |  |  \/   |  | |  |
// |  |'.'|  |\_) |  |\|  ||     ' _)\_) |  |\|  | '..`''.) |  |_|( OO )/_) |OO  ) |  |(_/\_) |  |\|  |
// |  |   |  |  \ |  | |  ||  .   \    \ |  | |  |.-._)   \ |  | | `-' /||  |`-'| ,|  |_.'  \ |  | |  |
// |  |   |  |   `'  '-'  '|  |\   \    `'  '-'  '\       /('  '-'(_.-'(_'  '--'\(_|  |      `'  '-'  '
// """    """     """""""" """  """"      """""""  """""""  """"""""      """"""   """         """""""
 

//Mahir Ratanpara (DA-IICT)
#include<bits/stdc++.h>
using namespace std;
#define Ff(i,a,n) for(i=a;i<n;i++)
#define Fr(i,a,n) for(i=a;i>n;i--)
#define ll long long
#define FAST ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);
#define pb push_back
#define ff first
#define ss second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define sortall(x) sort(all(x))
#define tr(it, a) for(auto it = a.begin(); it != a.end(); it++)
typedef pair<ll, ll>	pa;
typedef vector<ll>		vc;
typedef vector<pa>		vp;
typedef vector<vc>		vvc;
int mpow(int base, int exp); 
void ipgraph(ll n,ll m);
void dfs(int u, int par);
const int mod = 1000000007;
const int N = 3e5, M = N;
//=======================

vc g[N];

int main() {
    FAST;
    ll t, i, j, k, p, q, r, x, y, u, v, n, m;
    cin>>n>>x>>t;
	y=n/x;
	if(n%x>0)
	y++;
	cout<<y*t;
    return 0;
}

int mpow(int base, int exp) {
  base %= mod;
  int result = 1;
  while (exp > 0) {
    if (exp & 1) result = ((ll)result * base) % mod;
    base = ((ll)base * base) % mod;
    exp >>= 1;
  }
  return result;
}

void ipgraph(ll n, ll m){
	int i, u, v;
	while(m--){
		cin>>u>>v;
		g[u-1].pb(v-1);
		g[v-1].pb(u-1);
	}
}

void dfs(int u, int par){
	for(int v:g[u]){
		if (v == par) continue;
		dfs(v, u);
	}
}