#include <stdio.h>

#define N 1000001

int n,v[N],max,e;

void citire()
{
	scanf("%d",&n);
	scanf("%d",&v[0]);
	if(v[0]!=0)
		++e;
	for( int i=1 ; i<n ; ++i )
	{
		scanf("%d",&v[i]);
		if(v[i]!=0 && v[i-1]==0)
			++e;
		if(v[i]>max)
			max=v[i];
	}
	if(e==0)
		printf("%d",max);
	else
		printf("%d",max*e);
}

int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	citire();
	return 0;
}