#include<stdio.h>
long long x[10000001],i,j,k,n,l,s;
int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	scanf("%lld",&n);
	for (i=1;i<=n;i++)
	scanf("%lld",&x[i]);
	for (i=1;i<=n;i++)
	{
		j=i;
		while (x[j]<=x[j+1]&&j<=n) j++;
		s+=(x[j]-k);
		while (x[j]>=x[j+1]&&j<=n) j++;
		k=x[j];
		i=j-1;
	}

	printf("%lld\n",s);
	return 0;
}