#include <bits/stdc++.h>

using namespace std;

#define int long long
// typedef long long ll;
const int N = 1e6 + 7;
int ai[N];
int bi[N];
queue<int>q;
void solve()
{
	int n,m;
	cin >> n >> m;
	int sum = 0;
	for(int i = 1; i <= n; i++) {
		cin >> ai[i];
		bi[ai[i] % m]++;
		if(bi[ai[i] % m] == 2) sum++;
	}
	if(sum == 1) {
		if(ai[i] % m == 0) cout << "0";
		else cout << "1";
	}else if(sum == 2) {
		for(int i = 2; i <= n; i++) {
			if(ai[i] % m == ai[i - 1] % m) {
				cout << "-1\n";
				return;
			}
		}
		cout << "2\n";
	}else cout << "-1";
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int tt;
	tt = 1;
	// cin >> tt;
	while (tt--)
	{
		solve();
	}
}

answer.code: In function ‘void solve()’:
answer.code:22:23: error: ‘i’ was not declared in this scope
   22 |                 if(ai[i] % m == 0) cout << "0";
      |                       ^