Problem:
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Maximum Profit

You can obtain profits from foreign exchange margin transactions. For example, if you buy 1000 dollar at a rate of 100 yen per dollar, and sell them at a rate of 108 yen per dollar, you can obtain (108 - 100) × 1000 = 8000 yen.

Write a program which reads values of a currency $R_t$ at a certain time $t$ ($t = 0, 1, 2, ... n-1$), and reports the maximum value of $R_j - R_i$ where $j > i$ .

Input

The first line contains an integer $n$. In the following $n$ lines, $R_t$ ($t = 0, 1, 2, ... n-1$) are given in order.

Output

Print the maximum value in a line.

Constraints

$2 \leq n \leq 200,000$

$1 \leq R_t \leq 10^9$

Sample Input 1

6
5
3
1
3
4
3

Sample Output 1

3

Sample Input 2

3
4
3
2

Sample Output 2

-1

Solution in C++ (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n) for (ll i = 0; i < (ll)n; i++)
#define all(x) (x).begin(), (x).end()
#define unique(x) x.erase(unique(x.begin(), x.end()), x.end());
const long long INF = 1LL << 60;
// map<int,int> mp;

int main() {
  // in

  int N;
  cin >> N;
  vector<int> R(N);

  for (int i = 0; i < N; i++) {
    cin >> R[i];
  }

  // pro

  int pp, dif;

  pp = R[0];

  dif = R[1] - R[0];

  for (int i = 1; i < N; i++) {
    dif = max(dif, R[i] - pp);

    pp = min(pp, R[i]);
  }

  // out

  cout << dif << endl;
}