#include <bits/stdc++.h>

using namespace std;

typedef long long int ll;
typedef pair<ll, ll> pll;

#define FOR(i, n, m) for(ll (i)=(m);(i)<(n);++(i))
#define REP(i, n) FOR(i,n,0)
#define OF64 std::setprecision(40)

const ll MOD = 1000000007;
const ll INF = (ll) 1e15;

ll A[2005];

ll gcd(ll a, ll b) {
    if (a < b)
        swap(a, b);
    ll c = a % b;
    if (c == 0)
        return b;
    return gcd(b, c);
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N;
    cin >> N;
    REP(i, N) {
        cin >> A[i];
    }
    ll mn = INF;
    REP(i, N) {
        mn = std::min(mn, A[i]);
    }
    std::unordered_map<ll, ll> mp;
    REP(i, N) {
        ll n = 1;
        while (n * n <= A[i] && n <= mn) {
            if (A[i] % n == 0) {
                {
                    auto it = mp.find(n);
                    if (it == mp.end()) {
                        mp[n] = A[i];
                    }
                    else {
                        it->second = gcd(it->second, A[i]);
                    }
                }
                ll x = A[i] / n;
                if (x <= mn) {
                    auto it = mp.find(x);
                    if (it == mp.end()) {
                        mp[x] = A[i];
                    }
                    else {
                        it->second = gcd(it->second, A[i]);
                    }
                }
            }
            n++;
        }
    }
    ll ans = 0;
    for (auto &p : mp) {
        if (p.first == p.second)
            ans++;
    }
    cout << ans << endl;
    return 0;
}
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define Pint pair<int,int>
#define Pll pair<ll,ll>
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<n;i++)
#define all(v) v.begin(),v.end()
#define pb push_back
#define eb emplace_back
template<class T>void chmax(T &a,T b){if(a<b)a=b;}
template<class T>void chmin(T &a,T b){if(a>b)a=b;}
constexpr int INF=1000000000;
constexpr ll llINF=1000000000000000000;
constexpr int mod=1000000007;
constexpr double eps=1e-8;
const double pi=acos(-1);
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
int Random(int mi,int ma){
    random_device rnd;
    mt19937 mt(rnd());//32bit
    //[mi,ma]
    uniform_int_distribution<int>engine(mi,ma);
    return engine(mt);
}
ll gcd(ll a,ll b){
    if(b==0)return a;
    return gcd(b,a%b);
}
ll lcm(ll a,ll b){
    return a/gcd(a,b)*b;
}
bool prime(int a){
    if(a==1)return false;
    for(int i=2;i*i<=a;i++){
        if(a%i==0)return false;
    }
    return true;
}
ll modpow(ll a,ll b){
    if(b==0)return 1;
    if(b%2)return modpow(a,b-1)*a%mod;
    ll memo=modpow(a,b/2);
    return memo*memo%mod;
}
vector<ll>kaijo,invkaijo;
void init_fact(int n){
    kaijo.resize(n+1);
    invkaijo.resize(n+1);
    kaijo[0]=1;
    for(ll i=1;i<=n;i++){
        kaijo[i]=kaijo[i-1]*i;
        kaijo[i]%=mod;
    }
    rep(i,n+1)invkaijo[i]=modpow(kaijo[i],mod-2);
}
vector<vector<ll>>C,sC;
void init_comb(int n,int m){
    C.resize(n+1,vector<ll>(m+1,0));
    sC.resize(n+1,vector<ll>(m+1,0));
    C[0][0]=1;
    for(int i=1;i<=n;i++){
        C[i][0]=1;
        for(int j=1;j<=m;j++){
            C[i][j]=(C[i-1][j-1]+C[i-1][j])%mod;
        }
    }
    rep(i,n+1){
        rep(j,m){
            sC[i][j+1]=(sC[i][j]+C[i][j])%mod;
        }
    }
}
ll comb(int a,int b){
    if(a<b)return 0;
    if(a<0||b<0)return 0;
    return kaijo[a]*invkaijo[a-b]%mod*invkaijo[b]%mod;
}
ll inv(ll x){
    x=modpow(x,mod-2);
    return x;
}
void solve(){
    int n;
    string s[110];
    cin>>n;
    rep(i,n)cin>>s[i];
    int d[110][110];
    rep(i,n){
        rep(j,n){
            if(s[i][j]=='1')d[i][j]=1;
            else if(i==j)d[i][j]=0;
            else d[i][j]=INF;
        }
    }
    rep(k,n){
        rep(i,n){
            rep(j,n){
                chmin(d[i][j],d[i][k]+d[k][j]);
            }
        }
    }
    double ans=0;
    rep(i,n){
        int c=0;
        rep(j,n){
            if(d[j][i]<INF)c++;
        }
        ans+=1.0/c;
    }
    printf("%.12lf\n",ans);
}
int main(){
    //int t;cin>>t;while(t--)
    solve();
    return 0;
}