#include<fstream.h>
int main(){
long nr,n,v[100],max,i;
ifstream f("operatii.in");
ofstream g("operatii.out");
f>>n;
for(i=1;i<=n;i++)f>>v[i];
max=0; nr=0;
v[i+1]=0;
for(i=2;i<=n;i++)if(v[i]==0){nr=nr+max;max=0;}
		 else{if(v[i]>max)max=v[i]; }
g<<nr;}