t = int(input())
x,a = map(int,input().split())
y,b = map(int,input().split())

import heapq
#ダイクストラ法
m = 10**7
INF = 10**15
dist = [INF]*(2*m+1)
que = [(0,m)]
dist[m] = 0
while que:
  c,crr = heapq.heappop(que)
  if c > dist[crr]: continue
  if crr == t+m: print(c); exit()
  for c,d in [(1,1), (x,a), (y,-b)]:
    nxt = crr + d
    if nxt >= 2*m+1: continue
    if nxt < 0: continue
    if dist[crr] + c < dist[nxt]:
      dist[nxt] = dist[crr] + c
      heapq.heappush(que,(dist[nxt],nxt))

print(dist[t+m])