#include <cstdio>
using namespace std;
int v[100005];
int d[100005];
int main()
{
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    int n ,i;
    scanf("%d",&n);
    for(i=1;i<=n;i++)scanf("%d",&v[i]);
    d[1]=v[1]+v[2];
    for(i=2;i<n-1;i++)
    {
        int v1=d[i-3]+v[i]+v[i+1];
        int v2 =d[i-1];
        if(v1<v2)d[i]=v2;
        else
            d[i]=v1;
    }
    printf("%d\n",d[n-2]);
    return 0;
}