Submission #7076587

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <iomanip> // cout<<setprecision(n)
#include <functional> // std::function<void(ll)>
using namespace std;
#define All(v) (v).begin(),(v).end()
typedef long long ll;
const ll mod = 1000000007;
const ll inf = mod*mod;
const ll d5 = 114514;
const double EPS = 1e-10;
const double INF = 1e+10;
const double PI = acos(-1.0);
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll N;
    cin>>N;
    vector<ll> c(N);
    for(ll i=0;i<N;i++)cin>>c[i];
    double res=0;
    for(ll i=0;i<N;i++){
        int cnt=0;
        for(ll j=0;j<N;j++){
            if(i==j)continue;
            if(c[i]%c[j]==0)cnt++;
        }
        if(cnt%2==1)res+=(cnt+2.0)/(2*cnt+2.0);
        else res+=0.5;
    }
    cout<<setprecision(10)<<res<<endl;
}

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