#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main()
{
    int N;
    cin >> N;
    vector<int> vec(N, 0);
    vector<int> memo(N, 0);
    for(int i = 0; i < N; i++)
        cin >> vec[i];

    memo[0] = vec[0] / 2;

    for(int i = 1; i < N; i++)
    {
        memo[i] = memo[i - 1] + vec[i] / 2;
    }

    int ans = 0;

    for(int i = 0; i < N; i++)
    {
        ans = max(memo[N - 1] + vec[i] - vec[i] / 2 , ans);    
    }

    cout << ans << endl;
}