#include <iostream>

int suma(int v[], int st, int dr){
    if(st==dr) return v[st];
    else{
        int m = (st+dr)/2;
        int s1 = suma(v,st,m);
        int s2 = suma(v,m+1,dr);
        return s1+s2;
    }
}
int main(){
    int v[1001], n;
    std::cin >> n;
    for(int i=1; i<=n; i++)
        std::cin >> v[i];
    std::cout<< suma(v,1,n);
}