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

x, N = divmod(N, (12 + Q) * M)

if N <= (P - 1) * M:
    print((N - 1) // M + 1 + x * 12)
    
elif N <= (P - 1) * M + Q * 2 * M:
    
    print((N - (P - 1) * M - 1) // (2 * M) + P + x * 12)
    
else:
    
    print((N - (P - 1) * M - Q * 2 * M - 1) // M + P + Q + x * 12)