#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("unroll-loops") 
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp> 
#define int long long
#define fr(i,a,b) for(int i = a ; i <= b ; ++i)
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()
#define pb push_back
#define fst first
#define snd second
using namespace __gnu_pbds;
using ordered_set =
 tree<int, null_type,less<int>,
 rb_tree_tag,tree_order_statistics_node_update>;
//find_by_order(k):returns iterator to kth element starting from 0
//order_of_key(k):returns count of elements strictly smaller than k
typedef long long ll;typedef pair<int, int> pii;
typedef vector<int> vi;typedef long double ld;
template<class T>
using min_heap = priority_queue<T,vector<T>,greater<T>>; 
template<typename T> T gcd(T a, T b){return(b?__gcd(a,b):a);}
template<typename T> T lcm(T a, T b){return(a*(b/gcd(a,b)));}
template<class T> void re(T& x) { cin >> x; }
template<typename T> 
void remdup(vector<T>& v) {
	sort(all(v)); v.erase(unique(all(v)), v.end());
}
template<typename T> void re(vector<T> &v) {trav(i,v) cin >> i;}
template<class H, class... T> void re(H& h, T&... t) { re(h); re(t...); }
void unsyncIO() { ios_base::sync_with_stdio(0); cin.tie(0); }
#ifdef np
#include "/home/o_o/MyCodes/pr.h"
#else
#define trace(...)
#endif

#define MOD 1000000007  

void solve(){
	int cnt = 1 ;
	int n , x , t ;
	re(n,x,t);
	while(cnt*x<n) cnt++;
	cout << cnt * t << endl; 
}

signed main() {
	unsyncIO();
	int tt =1 ;
	// cin >> tt;
	rep(i,0,tt) solve();













#ifdef np
	cout <<endl<<endl<< "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
	return 0;
}

 #include<bits/stdc++.h>
 // #include <ext/pb_ds/tree_policy.hpp>
 // #include <ext/pb_ds/assoc_container.hpp>
 #include<chrono>
  using namespace std;
   using namespace std::chrono;      
  // using namespace __gnu_pbds; 
 #define fastio     ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
 #define fi         first
 #define se         second
 #define int         long long 
 #define pb         push_back
 #define emp        emplace_back
 #define vv(x)      vector<x>
 #define mp(x,y)    map<x,y>
 #define dq(x)      deque<x>
 #define pql(x)     priority_queue<x>
 #define pqs(x)     priority_queue<x,vv(x),greater<x> >
 //#define M          1000000007
 #define forf(i,a,b) for(int i=a;i<b;i++)
 #define it(x)      x::iterator
 #define ll         long long 
 #define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
 #define time__(d)  for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false); debug("%s time : %.4fs", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))
 #define vii        vector<int>
 #define big        1e12
 #define sm         -2e18
 #define mkr        make_pair
 #define vpi        vector<pair<int,int> >
 #define pii        pair<int,int>
 #define rng        500005
 #define sz(x)      (int)x.size()
 #define rv(x)      reverse(x.begin(),x.end())
 #define out(x)     cout<<x.fi<<" "<<x.se<<endl;
#define MEM(x,val) memset(x,val,sizeof(x))

 // typedef tree<pii, null_type, less<pii>, rb_tree_tag,  
 //            tree_order_statistics_node_update>  odst; 


void pr_init()
{
   
    #ifndef ONLINE_JUDGE
    freopen("gin.txt", "r", stdin);
   // freopen("output.txt", "w", stdout);
   
    #endif
}


void solve()
{
  int n,x,t;
  cin >> n >> x >> t;

  int an = ceil((double)n/(double)x)*t ;
  cout<<an;  

}

int32_t main()
{
  pr_init();
  fastio;
  auto start = high_resolution_clock::now(); 
  solve(); 
  auto stop = high_resolution_clock::now();
  auto duration = duration_cast<microseconds>(stop - start); 
  
    // cout << "Time taken by function: "
    //      << duration.count() << " microseconds" << endl; 

  return 0;
}