b3.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
  int n, cnt = 0;
  double a[50], sum = 0;
  cout << "Nhap n: "; cin >> n;
  for (int i = 0; i < n; i++) {
    cout << "Nhap a[" << i << "]: "; cin >> a[i];
    if (a[i] > 0) {
      sum += a[i];
      cnt++;
    }
  }
  cout << "TBC cac phan tu duong la: " << sum / cnt << endl;
}