#include<stdio.h>
#define nmax 1000001
long long i,j,a,b,n,max,s,scade,min=99999,k;
int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);

	scanf("%lld\n",&n);

	for(i=1;i<=n;i++)
	{
		scanf("%lld",&a);
		if(!scade&&max<a)
			max=a;
		if (min>a)
			min=a;
		if(a<b)
			scade=1;
		if(scade && a>b)
		{
			s+=max;
			k++;
			if(k>1)
				s-=min;
			scade=0;
			max=0;
			min=b;
			if(max<a)
				max=a;

		}
		b=a;
	}
	s+=max;
	if(k>1)
		s-=min;
	printf("%lld",s);

	return 0;

}