#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define ll long long
#define ll_MAX LONG_LONG_MAX
#define ll_MIN LONG_LONG_MIN
#define pi pair<int,int>
#define endl "\n"
#define MAXN 100005
#define mod 1000000007
using namespace std;

void solve()
{
    
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
	cout.tie(NULL);
    solve();
    ll n,x,t;
    cin>>n>>x>>t;
    if(n%x)
    {
        cout<<(n/x + 1)*t<<'\n';
    }
    else
    {
        cout<<(n/x)*t<<'\n';
    }
}
#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string>
#include <vector>
#include <cctype>
#include <cstdio>
#include <iomanip>
 
using namespace std;
 
string in, t;
double a, b, c, d;
 
 
int main(){
    cin >> a >> c >> b >> d;
    cout << fixed << setprecision(5) << sqrt(fabs(a - b)*fabs(a - b)*1.0 + fabs(c - d)*fabs(c - d)*1.0) << endl;
}