N, M, P, Q = map(int, input().strip().split())

ans, N = (N // ((12 + Q) * M)) * 12, N % ((12 + Q) * M)

for i in range(12):
  if N <= 0:
    break
  
  N = N - M - (M if P <= i+1 <= P+Q-1 else 0)
  ans += 1

print(ans)