#include<fstream.h>
int v[1000],i,n,k,s;
int main()
{
ifstream f("operatii.in");
ofstream g("operatii.out");
f>>n;
for(i=0;i<n;i++)f>>v[i];
for(i=0;i<n;i++){while(v[i]){if(v[i]>s)s=v[i];i++;}k+=s;s=0;}
g<<k;
f.close();
g.close();
return 0;
}