#include<stdio.h>
using namespace std;

 int main()
 { long long nr,n,max,a,ok,i;
	 
	 FILE *f = fopen("operatii.in", "r");
	 FILE *g = fopen("operatii.out", "w");
	
	 nr = 0;
	 fscanf(f, "%lld", &n);
	
	 for( i = 1; i <= n; i++ )
		 {
			 fscanf(f, "%lld", &a);
			 max = ok = 0;
			 while(a != 0)
				 {
					 if(a > max) max = a, ok = 1;
					 fscanf(f, "%lld", &a); i++;
					 if(i > n) break;
				 }
			 if(ok) nr += max;
		 }
	 
	 fprintf(g, "%d\n", nr);
	 
	 fclose(f);
	 fclose(g);
	 return 0;
 }