#include <bits/stdc++.h>

#define int long long
#define lowbit(x) ((x) & (-x))
#define rep(i, s, t, st) for (int i = s, __##i = t; i <= __##i; i += st)
#define per(i, s, t, st) for (int i = s, __##i = t; i >= __##i; i -= st)
#define gc getchar
#define pll pair<int, int>
#define clr(pst, siz) memset(pst, 0, sizeof(int) * siz)
#define cpy(pst, tar, siz) memcpy(pst, tar, sizeof(int) * siz)

inline int read()
{
  int x = 0, f = 1, ch = gc();
  while (!isdigit(ch))
  {
    if (ch == '-')
      f = -f;
    ch = gc();
  }
  while (isdigit(ch))
  {
    x = (x << 1) + (x << 3) + ch - '0';
    ch = gc();
  }
  return x * f;
}
inline void write(int x)
{
  if (x < 0)
    putchar('-'), x = -x;
  if (x / 10)
    write(x / 10);
  putchar('0' + x % 10);
}

struct Edge
{
  int u, v, weight;
  bool operator<(const Edge &e) const
  {
    return weight < e.weight;
  }
};
class UnionFind
{
public:
  int parent[1010], rank[1010];
  UnionFind(int n)
  {
    rep(i, 0, n - 1, 1)
    {
      parent[i] = i;
      rank[i] = 0;
    }
  }

  int find(int x)
  {
    if (x != parent[x])
      parent[x] = find(parent[x]);
    return parent[x];
  }

  bool unite(int x, int y)
  {
    int rootX = find(x);
    int rootY = find(y);
    if (rootX != rootY)
    {
      if (rank[rootX] > rank[rootY])
        parent[rootY] = rootX;
      else if (rank[rootX] < rank[rootY])
        parent[rootX] = rootY;
      else
      {
        parent[rootY] = rootX;
        rank[rootX]++;
      }
      return true;
    }
    return false;
  }
};

int a[1010];
Edge e[1000010];

signed main()
{
#ifndef ONLINE_JUDGE
  freopen("mst.in", "r", stdin);
  freopen("mst.out", "w", stdout);
#endif
  int n = read();
  rep(i, 0, n - 1, 1) a[i] = read();
  int cnt = 0;
  rep(i, 0, n - 1, 1)
      rep(j, i + 1, n - 1, 1) if (a[i] > a[j])
          e[cnt++] = {i, j, a[i] - a[j]};
  std::sort(e, e + cnt);
  UnionFind uf(n);
  int mst_weight_sum = 0;
  int selected_edges = 0;
  for (int i = 0; i < cnt; ++i)
  {
    const Edge &edge = e[i];
    if (uf.unite(edge.u, edge.v))
    {
      mst_weight_sum += edge.weight;
      selected_edges++;
      if (selected_edges == n - 1)
        break;
    }
  }
  write(mst_weight_sum);
  putchar('\n');
  return 0;
}