#include <bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
double arr_avg(vector<int>& arr, int idx) {
if (idx == arr.size()) return 0;
return double(arr[idx]) / arr.size() + arr_avg(arr, idx + 1);
}
void solve() {
vector<int> arr = {1,8,2,10,3};
cout << arr_avg(arr, 0) << endl;
}
int main() {
IOS;
solve();
return 0;
}
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