1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
#include <bits/stdc++.h>
#define dbg(x) " [" << #x << ": " << (x) << "] "
using namespace std;
using ll = long long;
template<typename A, typename B>
ostream& operator<<(ostream& out, const pair<A,B>& p) {
    return out << "(" << p.first << ", " << p.second << ")";
}
template<typename T>
ostream& operator<<(ostream& out, const vector<T>& c) {
    out << "{";
    for(auto it = c.begin(); it != c.end(); it++) {
        if(it != c.begin()) out << ", ";
        out << *it;
    }
    return out << "}";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int w, h, n;
    cin >> w >> h >> n;
    vector<int> d(n);
    for(int i = 0; i < n; i++) cin >> d[i];
    if(w % d[0] != 0 || h % d[0] != 0) {
        cout << -1 << endl;
        return 0;
    }

    ll x = 0, y = 0;
    ll ans = 0;
    for(int i = n - 1; i >= 0; i--) {
        ll a = w / d[i];
        ll b = h / d[i];
        ans += a * b - x / d[i] * y / d[i];
        x = a * d[i];
        y = b * d[i];
    }
    cout << ans << endl;

    return 0;
}