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
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

long long pow(long long x, int y, int d) {
	x -= x%d;
	y -= y%d;
	return x * y;
}

int main() {
	int x,y,n, d[31];
	scanf("%d %d %d", &x, &y, &n);
	for (int i = 0; i < n; i++) scanf("%d", &d[i]);
	if (x % d[0] != 0 || y % d[0] != 0) {
		puts("-1");
		return 0;
	}
	long long ret = 0;
	for (int i = 0; i < n; i++) {
		ret += (pow(x, y, d[i]) - pow(x, y, (i == n-1 ? x+1 : d[i+1]))) / (((long long)d[i]) * d[i]);
	}
	printf("%lld\n", ret);
	return 0;
}