#include <fstream.h>

int main(){
    ifstream in("operatii.in");
    ofstream out("operatii.out");
    long long  n,sum=0,i,nr,max;
    in >>n;
    max=0;
    for(i=0;i<n;i++){
                     in >>nr;
                     if(nr==0)
                              if(max>0){
                                        sum+=max;
                                        max=0;
                              }   
                     if(nr>max)
                               max=nr;
                     if(i==n-1)
                               sum+=max;
                     /*if(max>0)          
                                        if(nr==0 || i==n-1){
                                                  sum=sum+max;
                                                  max=0;
                                        }*/
    }
    out <<sum;
    in.close();
    out.close();
    return 0;
}