output_description: Print the minimum amount of money required to generate the substance C. If it
  is not possible to generate the substance C, print `-1` instead.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N M_a M_b  
      a_1 b_1 c_1  
      a_2 b_2 c_2
      :  
      a_N b_N c_N
attempt: def solve():
      
      INF = float('inf')
      
      N, Ma, Mb = map(int, input().split())
      
      l = []
      for _ in range(N):
          a,b,c = map(int, input().split())
          l.append((a,b,c))
          
      #dp table: dp[i][ca][cb] 
      dp = [[[INF] * 401 for _ in range(401)] for _ in range(N+1)]
      dp[0][0][0] = 0
      
      for i in range(N):
          for ca in range(401):
              for cb in range(401):
                  if dp[i][a][b] != INF:
                      dp[i+1][a][b] = min(dp[i][a][b], dp[i+1][a][b]) #薬品iを加えない場合
                      dp[i+1][a+l[i][0]][b+l[i][1]] = min(dp[i+1][a+l[i][0]][b+l[i][1]], dp[i][a][b] + l[i][2]) #薬品iを加える場合
                      
      ans = INF
      for i in range(N):
          for ca in range(401):
              for cb in range(401):
                  if dp[i][a][b] != INF:
                      if a * Mb == b * Ma:
                          ans = min(ans, dp[i][a][b])
      
      print(-1 if ans == INF else ans)
  
  if __name__ == '__main'__:
      solve()
problem_description: Statement
  
  Dolphin is planning to generate a small amount of a certain chemical substance
  C.  
  In order to generate the substance C, he must prepare a solution which is a
  mixture of two substances A and B in the ratio of M_a:M_b.  
  He does not have any stock of chemicals, however, so he will purchase some
  chemicals at a local pharmacy.  
  The pharmacy sells N kinds of chemicals. For each kind of chemical, there is
  exactly one package of that chemical in stock.  
  The package of chemical i contains a_i grams of the substance A and b_i grams
  of the substance B, and is sold for c_i yen (the currency of Japan).  
  Dolphin will purchase some of these packages. For some reason, he must use all
  contents of the purchased packages to generate the substance C.  
  Find the minimum amount of money required to generate the substance C.  
  If it is not possible to generate the substance C by purchasing any
  combination of packages at the pharmacy, report that fact.
samples: [{"input": "3 1 1\n    1 2 1\n    2 1 2\n    3 3 10", "output": "3\n    \n\nThe amount of money spent will be minimized by purchasing the packages of\nchemicals 1 and 2.  \nIn this case, the mixture of the purchased chemicals will contain 3 grams of\nthe substance A and 3 grams of the substance B, which are in the desired\nratio: 3:3=1:1.  \nThe total price of these packages is 3 yen.\n\n* * *"}, {"input": "1 1 10\n    10 10 10", "output": "-1\n    \n\nThe ratio 1:10 of the two substances A and B cannot be satisfied by purchasing\nany combination of the packages. Thus, the output should be `-1`."}]