#include<cstdio>
#include<iostream>

using namespace std;

int main(){

    int n, i, j;
    long long int a,first, last, higer;
    scanf("%i", &n);
    /*
    if(n > 2){
        x = n;
    }else{
        x = 
    }*/
    long long int sumas[((n-2)/2)+1];

    scanf("%lld", &first);
    sumas[0] = -1000000000;

    for(i = 1; i<n-1; i++){

        scanf("%lld", &a);
        //bloques[i] = a;

        if(i<=((n-2)/2)){

            sumas[i] = a;

        }

        else{
            
            if(a>sumas[0]){

                sumas[0] = a;
            }
        } 

        for(j = i/2; j>0; j--){

            if(!((i%j))){

                sumas[j]+=a;
            }

        }
    }

    scanf("%lld", &last);

    higer = -1000000000;

    bool ans = false;

    for(i = 0; i<((n-2)/2)+1; i++){

        if(sumas[i] > higer){

            higer = sumas[i];
            
        }
    }
    
    if(n <= 2){
        higer = 0;
    }   


    if(higer < 0){

        higer = 0;
    }

    printf("%lld", higer+first+last);

    

    return 0;
}