Submission #1318631

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <utility>
#define ll long long
#define INF 1000000000
#define mod 1000000007
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define all(x) (x).begin(),x.end()
using namespace std;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
bool debug=false;

int main(){
  int n,c[105]={0};
  double ans=0.0;
  cin>>n;
  rep(i,n)cin>>c[i];
  rep(i,n){
    int cnt=0;
    rep(j,n){
      if(i!=j&&c[i]%c[j]==0)cnt++;
    }
    if(cnt%2==1)ans+=0.5;
    else ans+=double(cnt+2)/(2*cnt+2);
  }
  printf("%.10f\n",ans);;
  return 0;
}

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