#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
int n, m, a[maxn], b[maxn];
long long k;

// 判断 <= x 的数是否 >= k 
bool check(long long x) {
	long long sum = 0;
	for (int i = 1; i <= n; i++) {
		if (a[i] >= 0) {
			// a[i]*b[1], a[i]*b[2], ..., a[i]*b[m] 升序 
			int l = 1, r = m, res = 0;
			while (l <= r) {
				int mid = (l + r) / 2;
				if ((long long)a[i] * b[mid] <= x)
					res = mid, l = mid + 1;
				else 
					r = mid - 1;
			}
			if (res) sum += res;
		}
		else {
			// a[i]*b[1], a[i]*b[2], ..., a[i]*b[m] 降序
			int l = 1, r = m, res = 0;
			while (l <= r) {
				int mid = (l + r) / 2;
				if ((long long)a[i] * b[mid] <= x)
					res = mid, r = mid - 1;
				else 
					l = mid + 1;
			}
			if (res) sum += m - res + 1;
		}
	}
	return sum >= k;
}

int main() {
	scanf("%d%d%lld", &n, &m, &k);
	for (int i = 1; i <= n; i++)
		scanf("%d", a+i);
	for (int i = 1; i <= m; i++)
		scanf("%d", b+i);
	sort(a+1, a+n+1);
	sort(b+1, b+m+1);
	long long l = -1e18, r = 1e18, res;
	while (l <= r) {
		long long mid = (l + r) / 2;
		if (check(mid)) 
			res = mid, r = mid - 1;
		else 
			l = mid + 1;
	}
	printf("%lld\n", res);
	return 0;
}