Submission #2170169

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Source Code Expand

#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<(b);i++)
#define erep(i,a,b) for(int i=a;i<=(int)(b);i++)
#define per(i,a,b) for(int i=(b)-1;i>(a);i--)
#define eper(i,a,b) for(int i=((int)(a));i>=b;i--)
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
const int INF=999999999;
const int MOD=1000000007;

int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0};
int gcd(int a,int b){return b?gcd(b,a%b):a;}

int n, c[100];

int main() {
    cin >> n;
    rep(i, 0, n) cin >> c[i];
    double ans = 0.0;
    rep(i, 0, n) {
        int cnt = 0;
        rep(j, 0, n) 
            if (i != j && c[i]%c[j] == 0) cnt++;
        ans += (double)(cnt/2 + 1)/(cnt+1);
    }
    printf("%.12f\n", ans);
    return 0;
}

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