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

using namespace std;

int n;
vector<int>arak;
vector<pair<int,int> > dp;

int main()
{
    cin>>n;
    arak.resize(n+1);
    dp.resize(n+1);
    for(int i=1;i<=n;i++)  cin>>arak[i];
    dp[1]=make_pair(arak[1],arak[1]);
    for(int i=2;i<=n;i++)
    {
        dp[i].first=min(dp[i-1].first,dp[i-1].second)+arak[i];
        dp[i].second=dp[i-1].first;
    }
    /*cout<<endl;
    for(int i=1;i<=n;i++) cout<<dp[i].first<<" ";
    cout<<endl;
    for(int i=1;i<=n;i++) cout<<dp[i].second<<" ";*/
        cout<<dp[n].first;
    return 0;
}