#include <iostream>
#include <fstream>   

using namespace std;

int main() {

	int n, x, t;

	cin >> n >> x >> t;

	int time = 0;
	while (n > 0) {
		time = time + t;
		n = n - x;
	}
	cout << time;

	return 0;
}
#include <iostream>
#include <cmath>

using namespace std;

int main() {
    int N, X, T;
    cin >> N >> X >> T;

    cout << (int)(ceil(1.0*N / X) * T) << endl;

    return 0;
}