#include<bits/stdc++.h> using namespace std; int main(){ //简单逆推 int N = 0; while(cin >> N){ vector<int> en_list; int copy_num = N; while(copy_num-- >0){ int en; cin >> en; en_list.push_back(en); } int start = 0; for(int i = en_list.size()-1;i>=0;i--){ int sum = en_list.at(i)+start; if(sum%2 == 0)start = sum/2; else start = (sum+1)/2; } cout << start << endl; } return 0; }