output_description: Print the maximum value in a line.
input_description: The first line contains an integer $n$. In the following $n$ lines, $R_t$ ($t
  = 0, 1, 2, ... n-1$) are given in order.
attempt: R = [int(input()) for i in range(int(input()))]
  dfmx = -(10**10)
  mn = 10**10
  for i in range(len(R)):
      dfmx = max(R[i] - mn, dfmx)
      mn = min(R[i], mn)
  print(dfmx)
  
problem_description: 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
  $j > i$ .
samples: [{"input": "6\n    5\n    3\n    1\n    3\n    4\n    3", "output": "3"}, {"input": "3\n    4\n    3\n    2", "output": "-1"}]