#include <bits/stdc++.h>   using namespace std;   int32_t main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     long long t;     t = 1;     for (long long test = 1; test <= t; test++) {       long long n;       cin >> n;       vector<long long> a;       for (long long i = 0; i <= n - 1; i++) {         long long x;         cin >> x;         if (x != 0) a.push_back(x);       }       long long bits[61] = {0};       n = a.size();       for (long long i = 0; i <= n - 1; i++) {         long long temp = a[i];         long long j = 0;         while (temp > 0) {           if (temp & 1) bits[j]++;           temp = temp >> 1;           j++;         }       }       for (long long i = 0; i <= 60; i++)         if (bits[i] >= 3) {           cout << 3;           exit(0);         }       long long cyclec = -1;       vector<vector<long long>> adj(n);       for (long long i = 0; i < n; i++)         for (long long j = i + 1; j < n; j++)           if ((a[i] & a[j]) != 0) {             adj[i].push_back(j);             adj[j].push_back(i);           }       for (long long i = 0; i <= n - 1; i++)         if (adj[i].size() != 0) {           vector<long long> dis(n, -1);           vector<long long> par(n, -1);           queue<long long> q;           q.push(i);           dis[i] = 0;           par[i] = -1;           while (!q.empty()) {             auto x = q.front();             q.pop();             for (auto y : adj[x])               if (dis[y] == -1) {                 dis[y] = 1 + dis[x];                 par[y] = x;                 q.push(y);               } else if (y != par[x]) {                 if (cyclec == -1)                   cyclec = (dis[y] + dis[x] + 1);                 else                   cyclec = min(cyclec, dis[y] + dis[x] + 1);               }           }         }       cout << cyclec;     }     return 0;   }   