#include<bits/stdc++.h>
using namespace std;


int main()
{
    int n,x,y;
    scanf("%d%d%d",&n,&x,&y);
    printf("%d",(n+x-1)/x*y);
}
#include <iostream>
using namespace std;
 
int main(){
  int n,x,t;
  cin>>n>>x>>t;
  
  int ans = n/x * t;
  ans += (n%x != 0)? t:0;
  cout<<ans<<endl;
  return 0;
}