题目

思路：

#include<bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 2e5 + 5;
int a[maxn], b[maxn], c[maxn];
void solve(){
	int n, k;
	cin >> n >> k;
	int g = 0;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
		a[i] -= k;
		g = __gcd(g, abs(a[i]));
	}
	sort(a + 1, a + n + 1);
	if(g == 0){
		cout << "0\n";
		return;
	}
	if(a[1] <= 0 && a[n] >= 0){
		cout << "-1\n";
		return;
	}
	int res = 0;
	for(int i = 1; i <= n; i++){
		// cout << a[i] << ' ';
		res += abs(a[i]) / g;
	}
	cout << res - n << '\n';
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int T;
	cin >> T;
	while(T--){
		solve();
	}
}