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
61
62
63
64
65
66
67
68
/*
Things to notice:
1. do not calculate useless values
2. do not use similar names
 
Things to check:
1. submit the correct file
2. time (it is log^2 or log)
3. memory
4. prove your naive thoughts 
5. long long
6. corner case like n=0,1,inf or n=m
7. check if there is a mistake in the ds or other tools you use
8. fileio in some oi-contest

9. module on time 
10. the number of a same divisor in a math problem
11. multi-information and queries for dp and ds problems
*/
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pii pair<long long,long long>
#define mp make_pair
#define pb push_back
const int mod=998244353;
const int inf=0x3f3f3f3f;
const int INF=1e18;
int n;
int d[35];
int X,Y;
void solve()
{
	cin>>X>>Y;
	cin>>n;
	for(int i=1;i<=n;i++) cin>>d[i];
	if(X%d[1]||Y%d[1])
	{
		cout<<"-1\n";
		return;
	}
	int ans=0;
	for(int i=n;i>=1;i--)
	{
		int cnt=X/d[i];
		if(!cnt) continue;
		X%=d[i];
		int t=Y;
		for(int j=i;j>=1;j--)
		{
			int cnt2=t/d[j];
			t%=d[j];
			ans+=1LL*cnt*cnt2*(d[i]/d[j]);
		}
	}
	cout<<ans<<"\n";
}
signed main()
{
//	ios::sync_with_stdio(0);
//	cin.tie(0);
	int _=1;
//	cin>>_;
	while(_--) solve();
	return 0;
}