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 <iostream>
#include <vector>

using namespace std;

int main() {
  int n;
  cin >> n;

  vector<int> a(n);
  for(int i = 0; i < n; i++) {
    cin >> a.at(i);
  }

  long minVal, maxProfit ;
  minVal = min(a.at(0), a.at(1));
  maxProfit = a.at(1) - a.at(0);
  for(int i = 2; i < n; i++) {
    if(a.at(i) - minVal > maxProfit) {
      maxProfit = a.at(i) - minVal;
    }
    if(a.at(i) < minVal) {
      minVal = a.at(i);
    }
  }
  cout << maxProfit << endl;

  return 0;
}