#include <bits/stdc++.h>
using namespace std;
long long MOD = 1000000007;
long long POW(long long a, long long b, long long MMM = MOD) {
  long long ret = 1;
  for (; b; b >>= 1, a = (a * a) % MMM)
    if (b & 1) ret = (ret * a) % MMM;
  return ret;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) {
  if (a == 0 || b == 0) return a + b;
  return a * (b / gcd(a, b));
}
int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
int ddx[] = {0, 0, 1, 1, 1, -1, -1, -1}, ddy[] = {1, -1, 1, 0, -1, 1, 0, -1};
int main() {
  int n;
  scanf("%d", &n);
  priority_queue<long long, vector<long long>, greater<long long> > q;
  long long ans = 0;
  for (int(i) = (0); (i) <= (n - 1); (i) += (1)) {
    long long x;
    scanf("%lld", &x);
    if (q.empty())
      q.push(x);
    else {
      long long t = q.top();
      if (x > t) {
        q.push(x);
        q.pop();
        ans += x - t;
      }
      q.push(x);
    }
  }
  printf("%lld", ans);
}
