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>
int main(void){
   int n, R[200000], max, key, i, l, key2;
   scanf("%d", &n);
   for ( i = 0; i < n; i++ ) {
      scanf("%d", &R[i]);
   }
   max = R[1] - R[0]; /*printf("\n%d\n", max);*/
   for ( l = 1; l < n; l++ ) {
      key = R[l] - R[0];
      if ( max < key ) { max = key; /*printf("%d\n", key);*/ }
   }
   key2 = 0;
   for ( i = 1; i < n; i++ ) {
      if ( R[i] < R[key2] ) {
         for ( l = 1; l < n - i; l++ ) {
            key = R[i + l] - R[i];
            if ( max < key ) { max = key; /*printf("%d\n", key);*/ }
            key2 = i;
         }
      }
   }
   printf("%d\n", max);
   return 0;
}