#include <stdio.h>
long long sol;
int i, n, t, prev;
int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	scanf("%d",&n);
	for ( i=1 ; i<=n ; ++i )
	{
		scanf("%d",&t);
		if( t-prev>0 )
			sol += t-prev;
		prev = t;
	}
	printf("%lld\n", sol);
}