#include <stdio.h>
int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	int n,i,a[1000005],op=0,j,ok,max=0,facinik=0,modif;
	scanf("%d",&n);
	for (i=1; i<=n; i++)
		scanf("%d",&a[i]);
	for (i=1; i<=100000; i++)
	{
		ok=0;
		modif=0;
		for (j=1; j<=n; j++)
			if (a[j]>=i)
				if (ok==0)
				{
					ok=1;
					op++;
					modif=1;
				}
				else 
					facinik=0;
			else
				ok=0;
		if (modif==0)
			break;
	}
	printf("%d",op);
	return 0;
}