Submission #1676999

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Source Code Expand

#include<iostream>
#include<cstdio>
#include<vector>
#include<string>
#include<functional>
#include<queue>
#include<cmath>
#include<algorithm>
#include<bitset>
#include<utility>
#include<complex>
#include<cstdlib>
#include<set>
#include<cctype>

#define DBG cerr << '!' << endl;
#define REP(i,n) for(int (i) = (0);(i) < (n);++i)
#define rep(i,s,g) for(int (i) = (s);(i) < (g);++i)
#define rrep(i,s,g) for(int (i) = (s);i >= (g);--(i))
#define PB push_back
#define MP make_pair
#define FI first
#define SE second
#define SHOW1d(v,n) {for(int i = 0;i < (n);i++)cerr << v[i] << ' ';cerr << endl << endl;}
#define SHOW2d(v,i,j) {for(int a = 0;a < i;a++){for(int b = 0;b < j;b++)cerr << v[a][b] << ' ';cerr << endl;}cerr << endl;}
#define ALL(v) v.begin(),v.end()

using namespace std;

typedef long long ll;
typedef vector<int> iv;
typedef vector<iv> iiv;
typedef vector<string> sv;

int main()
{
	int n,tmp;
	cin >> n;
	iv v;
	int yaku[n+2] = {};
	
	REP(i,n)
	{
		cin >> tmp;
		v.PB(tmp);
	}
	
	REP(i,n)REP(j,n)
	{
		if(i != j)
		{
			if(v[i] % v[j] == 0)
			{
				yaku[i]++;
			}
		}
	}
	
	double ret = 0;
	REP(i,n)
	{
		if(yaku[i] != 0)
		{
			if(yaku[i] % 2 == 0)
			{
				ret += (double)(yaku[i]+2)/(2*(yaku[i]+1));
			}
			else
			{
				ret += 0.5;
			}
		}
		else
		{
			ret += 1;
		}
	}
	
	printf("%.9f\n",ret);
	
	return 0;
}

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