#include<stdio.h>

#define N 1000001

int v[N],n,fin[N];

void citire()
{
	int i;
	scanf("%d",&n);
	for( i=0 ; i<n ; ++i )
		scanf("%d",&fin[i]);
	/*printf("%d ",n);
	for( i=0 ; i<n ; ++i )
		printf("%d ",fin[i]);
	*/
}

bool bun()
{
	int i;
	for( i=0 ; i<=n ; ++i )
		if( v[i]<fin[i] )
			return 1;
	return 0;
}

void calcul()
{
	int r=0,i;
	while( bun() )
		for( i=0 ; i<n ; ++i )
			if( v[i] < fin[i] )
				for( ++r ; v[i] < fin[i] ; ++i )
					++v[i];
	printf("%d\n",r);
}

int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	citire();
	calcul();
	return 0;
}