#include<stdio.h>
const int maxn = 1000200;

int N,ST[maxn];

int main()
{
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	scanf("%d\n",&N);
	long long sol = 0;
	for(int i = 1;i <= N; ++i)
	{
		int x = 0;
		scanf("%d",&x);	
		if (ST[ST[0]] < x)
		{
			sol += (long long)-(ST[ST[0]] - x);
		}
		while(ST[ST[0]] < x && ST[0]) ST[0]--;
		ST[++ST[0]] = x;
	}
	printf("%lld\n",sol);

	return 0;
}