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
// clang-format off
#include<bits/stdc++.h>
using namespace std;
using LL=long long;
#define FOR(i,l,r) for(auto i=(l);i<=(r);++i)
#define REP(i,n) FOR(i,0,(n)-1)
#define ssize(x) int(x.size())
template<class A,class B>auto&operator<<(ostream&o,pair<A,B>p){return o<<"("<<p.first<<", "<<p.second<<")";}
template<class T>auto operator<<(ostream&o,T x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<(", ")+2*!i++<<e;return o<<"}";}
#ifdef DEBUG
#define debug(x...) cerr<<"["#x"]: ",[](auto...$){((cerr<<$<<"; "),...);}(x),cerr<<'\n'
#else
#define debug(...) {}
#endif
// clang-format on

int
main()
{
    cin.tie(0)->sync_with_stdio(0);
    LL h, w, n, score = 0;
    cin >> h >> w >> n;
    vector<LL> seq(n);
    for (auto& x : seq) cin >> x;

    // Not possible
    LL hmod = h % seq.front(), wmod = w % seq.front();
    if (hmod || wmod) {
        cout << "-1\n";
        return 0;
    }

    REP (ptr, n - 1) {
        // Calculate the next hmod, wmod
        hmod = h % seq[ptr + 1], wmod = w % seq[ptr + 1];

        // Make sure seq[ptr + 1] divides both w and h
        score += (hmod / seq[ptr]) * (w / seq[ptr]);
        h -= hmod;
        score += (wmod / seq[ptr]) * (h / seq[ptr]);
        w -= wmod;
    }
    score += (h / seq.back()) * (w / seq.back());
    cout << score << "\n";
    return 0;
}