#include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <cmath>
#include <string>
#include <sstream>
#include <iomanip>
#include <complex>
using namespace std;
 
#define ll long long
#define vvi vector< vector<int> >
#define vi vector<int>
#define All(X) X.begin(),X.end()
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define REP(i,n) for(int i=0;i<(int)(n);i++)
#define pb push_back
#define pii pair<int,int>
#define mp make_pair
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

int main(){
	double i, j, k, l;
	cin >> i >> j >> k >> l;
	cout << fixed << setprecision(8);
	cout << (double)sqrt(pow(i - k, 2.0) + pow(j - l, 2.0)) << endl;
}
#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define mp  make_pair
#define pb  push_back
#define endl "\n"
#define rep(i,a,n) for(int i=a;i<n;i++)
const int mod = 1e9 + 7;
void solve() {
	int n, x, t;
	cin >> n >> x >> t;
	int s = 0, c = 0;
	while (s < n) {
		s += x;
		c++;
	}
	cout << c*t;
}
int32_t main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output1.txt", "w", stdout);
#endif
	int t;
	t = 1;
	//cin >> t;
	while (t--) {
		solve();
	}
	return 0;
}
