Submission #2179841

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Source Code Expand

#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <functional>
#define REP(i, n) for(int i=0;i<n;++i)
#define INF 100000000

using namespace std;

int n;
vector<int> v;

int num(int i, int n, vector<int> v){
  int tmp = 0;
  REP(j, n){
    if(v[i] % v[j] == 0) ++tmp;
  }

  return tmp;
}

float f(int n){
  if(n % 2 == 0){
    return 0.5;
  }
  else{
    return (float)(n + 1) / (float)(2 * n);
  }
}
  
int main(){
  cin >> n;
  REP(i, n){
    int x;
    cin >> x;
    v.push_back(x);
  }

  float tmp=0;

  REP(i, n){
    tmp += f(num(i, n, v));
  }

  printf("%lf", tmp);
  
  return 0;
}

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