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| #include <algorithm>
#include <bitset>
#include <map>
#include <vector>
#include <string>
#include <cstring>
#include <iostream>
#include <cmath>
#include <stack>
#include <set>
#include <queue>
using namespace std;
const double eps = 1e-10;
const double pi = 3.1415926535897932384626433832795;
const double eln = 2.718281828459045235360287471352;
#define f(i, a, b) for (int i = a; i <= b; i++)
#define LL long long
#define IN freopen("in.txt", "r", stdin)
#define OUT freopen("out.txt", "w", stdout)
#define scan(x) scanf("%d", &x)
#define mp make_pair
#define pb push_back
#define sqr(x) (x) * (x)
#define pr1(x) printf("Case %d: ", x)
#define pn1(x) printf("Case %d:\n", x)
#define pr2(x) printf("Case #%d: ", x)
#define pn2(x) printf("Case #%d:\n", x)
#define lowbit(x) (x & (-x))
#define fi first
#define se second
#define sz(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define summ(a) (accumulate(all(a), 0ll))
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
int n, a[100000 + 99], lo[100000 + 9], f[100009][20],cnt;
int gcd(int ma,int mi){
return mi?gcd(mi,ma%mi):ma;
}
inline int rmq_gcd(int l,int r){
int k=lo[r-l+1];
return gcd(f[l][k],f[r-(1<<k)+1][k]);
}
int ck(int l,int r){
return rmq_gcd(l,r)==1;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> a[1];
f[1][0] = a[1];
cnt+=a[1]!=1;
for (int i = 2; i <= n; ++i)
{
cin >> a[i];
cnt+=a[i]!=1;
f[i][0] = a[i];
lo[i] = lo[i >> 1] + 1;
}
for (int j = 1; j <= 17; ++j)
{
for (int i = 1; i + (1 << j) - 1 <= n; ++i)
{
f[i][j] = gcd(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
}
}
if(!ck(1,n)){
cout<<"-1";
return 0;
}
int ans=0x3f3f3f3f;
for(int i=1;i<=n;++i){
if(!ck(i,n))continue;
int l=i,r=n;
while(l<r){
int mid=(l+r)>>1;
if(ck(i,mid))r=mid;
else l=mid+1;
}
if(r==i)ans=min(ans,cnt);
else ans=min(ans,r-i+cnt-1);
}
cout<<ans;
return 0;
}
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