#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
struct shu{
    long long w;
    int bh;
}a[200010];
int n,bj,s;
long long ans;
bool cmp(shu x,shu y)
{
    if(x.w==y.w) return x.bh<y.bh;
    else return x.w>y.w;
}
int main()
{
    freopen("matHS.in","r",stdin);
    freopen("matHS.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        scanf("%lld",&a[i].w);
        a[i].bh=i;
    }
    sort(a+1,a+n+1,cmp);
    bj=n;
    for(int i=1;i<=n;i++)
    {
        if(a[i].w!=a[1].w)
        {
            bj=i-1;
            break;
        }
    }
    for(int i=1;i<=bj;i++)
    {
        if(a[i].bh==a[i+1].bh-1)
        {
            int t=0;
            while(a[i].bh==a[i+1].bh-1)
            {
                t++;
                i++;
            }
            t++;
            if(t%2==1) s+=t/2+1;
            else s+=t/2;
        }
        else s++; 
    }
    ans=2*a[1].w+s;
    printf("%lld",ans);
    return 0;
}