#include<stdio.h>

int a,ant,i,n;
long long s;

int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	
	scanf("%d",&n);
	
	for(i=1;i<=n;i++)
	{
		scanf("%d",&a);
		
		if(a-ant>0)
			s+=a-ant;
		
		ant=a[i];
	}
	
	printf("%lld",s);
	
	return 0;
}