#include <bits/stdc++.h>
using namespace std;
#define f(i,k,n) for(int i=k; i<n; i++)
#define ll long long
const int inf = INT_MAX;

void solve()
{
    int n;
    cin>>n;
    int a[n];
    f(i,0,n)    cin>>a[i];
    vector<int> p;
    p.push_back(a[0]);
    p.push_back(a[0]+a[1]);
    f(i,2,n)    p.push_back(min(p[i-1],p[i-2])+a[i]);
    cout<<p[n-1];
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1;
    //cin>>t;
    while(t--)  solve();
    return 0;
}