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
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
#include <bits/stdc++.h>
#define pb push_back
#define ll long long
#define int long long
using namespace std;
ll ans = 0;
vector <int> d;


int readInt () {
	bool minus = false;
	int result = 0;
	char ch;
	ch = getchar();
	while (true) {
		if (ch == '-') break;
		if (ch >= '0' && ch <= '9') break;
		ch = getchar();
	}
	if (ch == '-') minus = true; else result = ch-'0';
	while (true) {
		ch = getchar();
		if (ch < '0' || ch > '9') break;
		result = result*10 + (ch - '0');
	}
	if (minus)
		return -result;
	else
		return result;
}

void s(int w, int h, int last) {
    for (; last >= 0; last--) {
        if (d[last] <= w && d[last] <= h) break;
    }
    auto dl = d[last];
    ans += ((w/dl) * (h/dl));
    if (w % dl != 0) s(w%dl, h-(h%dl), last-1);
    if (h % dl != 0) s(w-(w%dl), h%dl, last-1);
    if (w %dl != 0 && h % dl != 0) s(w%dl, h%dl, last-1);
}
signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int h = readInt();
    int w = readInt();
    
    int n = readInt();
    for (int i = 0; i < n; i++) {
        int di = readInt();
        d.pb(di);
    }
    if (w % d[0] != 0 || h % d[0]!= 0) {
        cout << -1 << endl;
        return 0;
    }
    s(w, h, d.size()-1);
    cout << ans << endl;
}