#include <iostream>

#include <sstream>

#include <algorithm>

#include <cstdio>

#include <math.h>

#include <set>

#include <map>

#include <queue>

#include <string>

#include <string.h>

#include <bitset>

#define REP(i,a,n) for(int i=a;i<=n;++i)

#define PER(i,a,n) for(int i=n;i>=a;--i)

#define hr putchar(10)

#define pb push_back

#define lc (o<<1)

#define rc (lc|1)

#define mid ((l+r)>>1)

#define ls lc,l,mid

#define rs rc,mid+1,r

#define x first

#define y second

#define io std::ios::sync_with_stdio(false)

#define endl '\n'

#define DB(a) ({REP(__i,1,n) cout<<a[__i]<<' ';hr;})

using namespace std;

typedef long long ll;

typedef pair<int,int> pii;

const int P = 1e9+7, P2 = 998244353, INF = 0x3f3f3f3f;

ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}

ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}

ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}

inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;}

//head

const int N = 3e5+10;

int n, mu[N], gpf[N], d[N], cnt[N];

vector<int> fac[N], dv, val;

queue<int> q;

void dfs(int d, int s, int num) {

	val[s] = num;

	if (d!=dv.size()) dfs(d+1,s,num),dfs(d+1,s|1<<d,num*dv[d]);

}

void solve(int x) {

	dv.clear();

	int t = x;

	while (t!=1) {

		int z = gpf[t];

		while (t%z==0) t/=z;

		dv.pb(z);

	}

	int mx = 1<<dv.size();

	val.resize(mx);

	dfs(0,0,1);

	REP(i,0,mx-1) {

		int y = val[i];

		int sum = 0, r = ~i&(mx-1);

		for (int j=r; j; j=(j-1)&r) {

			sum += mu[val[j]]*cnt[val[j]*y];

		}

		sum += mu[1]*cnt[y];

		if (sum&&!d[y]) {

			q.push(y);

			d[y] = d[x]+1;

		}

	}

}

int main() {

	mu[1] = gpf[1] = 1;

	REP(i,1,N-1) {

		if (!gpf[i]) for (int j=i;j<N;j+=i) gpf[j]=i;

		for (int j=i;j<N;j+=i) fac[j].pb(i);

		for (int j=2*i;j<N;j+=i) mu[j]-=mu[i];

	}

	scanf("%d", &n);

	REP(i,1,n) {

		int t;

		scanf("%d", &t);

		set<int> s;

		while (t!=1) s.insert(gpf[t]),t/=gpf[t];

		for (int x:s) t*=x;

		if (d[t]) continue;

		d[t] = 1;

		for (int x:fac[t]) ++cnt[x];

		q.push(t);

	}

	if (d[1]) return puts("1"),0;

	while (q.size()) {

		int x = q.front(); q.pop();

		solve(x);

	}

	printf("%d\n", d[1]?d[1]:-1);

}