#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
 int N,X,T;
 cin >> N >> X >> T;
 int ans = N/X;
 double mod = N%X;
 if(mod > 0){
 ans = ans + 1;
 }
  ans = ans * T;
 cout << ans << endl;
}
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
const int mod=1e9+7;
const int N=1e6+10;
void read(int &a)
{
    a=0;int d=1;char ch;
    while(ch=getchar(),ch>'9'||ch<'0') if(ch=='-') d=-1;
    a=ch^48;
    while(ch=getchar(),ch>='0'&&ch<='9') a=(a<<3)+(a<<1)+(ch^48);
    a*=d;
}
void read(ll &a)
{
    a=0;int d=1;char ch;
    while(ch=getchar(),ch>'9'||ch<'0') if(ch=='-') d=-1;
    a=ch^48;
    while(ch=getchar(),ch>='0'&&ch<='9') a=(a<<3)+(a<<1)+(ch^48);
    a*=d;
}
int main()
{
    int n,x,t;
    read(n),read(x),read(t);
    if(n%x==0) printf("%d\n",n/x*t);
    else printf("%d\n",(n/x+1)*t);
    return 0;
}
