#include <bits/stdc++.h>

using namespace std;

int a, b, c;

int main() {
    cin >> a >> b >> c;
    for (int i = a; i <= b; i++) {
        if (i % c == 0) {
            cout << i << endl;
            exit(0);
        }
    }
    cout << -1 << endl;
    return 0;
}