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 <stdio.h>
#include <limits.h>
#define MAX_N 200000
typedef long long ll;
ll max(ll a, ll b) {
  if(a < b) return b;
  return a;
}
int main() {
  ll n, R[MAX_N], mn = LLONG_MAX/2, ans = -LLONG_MAX;  
  int i;
  scanf("%lld", &n);
  for(i = 0; i < n; i++) scanf("%lld", R+i);
  for(i = 0; i < n; i++) {
    ans = max(ans, R[i] - mn);    
    if(R[i] < mn) mn = R[i];
  }
  printf("%d\n", ans);
  return 0;
}