#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, ary[100], sum = 0;
  cin >> N;
  for (int i = 0; i < N; i++) cin >> ary[i];
  sort(ary, ary + N);
  for (int i = 0; i < N; i++) {
    sum += (ary[i] + ary[i + 1]) / 2;
  }
  cout << sum << endl;
}
