#include <bits/stdc++.h>
using namespace std;

int main()
{
    //cout<<"Hello\n";
    int n,x;
    cin>>n;
    vector<int> v;
    vector<int> dp(n);
    for(int i=0;i<n;i++){
        cin>>x;
        v.push_back(x);
    }
    dp[n-1]=v[n-1];
    dp[n-2]=v[n-1]+v[n-2];
    
    /*for(int i:v){
        cout<<i<<"\n";
    }*/
    for(int i=n-3;i>=0;i--){
        //cout<<i+1<<" ";
        dp[i]=min(dp[i+1],dp[i+2]);
        dp[i]+=v[i];
        //cout<<dp[i]<<" "<<(dp[i+1]>dp[i+2]?2:1)<<"\n";
    }
    cout<<dp[0];
}