1025

// OK Timus 1025

# include <iostream>
# include <vector>
# include <algorithm>
using namespace std;

int main() {
    size_t n;
    size_t sum;
    sum = 0;
    cin >> n;
    vector<size_t> m(n);
    for (size_t i = 0; i < n; i++) {
        cin >> m[i];
    }
    sort(m.begin(), m.end());
    for (size_t i = 0; i < (n + 1) / 2; i++) {
        sum += (m[i] + 1) / 2;
    }
    cout << sum;
    return 0;
}