#include<stdio.h>
int n,max,s,a;
int main ()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
    int i;
    scanf("%d",&n);
    for(i=1;i<=n;++i)
    {
        scanf("%d",&a);
        if(a!=0)
        {
            if(max<a)
                max=a;
        }
        else
        {
            s+=max;
            max=0;
        }
	}
	s+=max;
    printf("%d",s);
    return 0;
}