#include<stdio.h>

long v[(1<<20)];


int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	
	long n;
	scanf("%ld",&n);
	
	long max = 0 , h = 0;
	long long sol = 0;
	
	
	for( long i = 1; i <= n; ++i )
	{
		scanf("%ld",&v[i]);
		
		if( v[i] > max) max = v[i];
		if( v[i] < v[i-1]) { sol+= (max-v[i]); max = v[i];}
	}
	sol+=max;
	printf("%lld\n",sol);
}