#include<fstream>
#include<stdio.h>
using namespace std;
int x, s, n, i, maxim;
FILE*fin=fopen("operatii.in","r");
ofstream fout("operatii.out");
int main(){
    fscanf(fin,"%d", &n);
    for(i=1; i<=n; i++){
        fscanf(fin,"%d", &x);
        if(x!=0){
            if(x>maxim)
                maxim=x;
        }
        else{
            s+=maxim;
            maxim=0;
        }
    }
    s+=maxim;
    fout<<s;
return 0;
}