NKTL=input()
N = ''
K = ''
T = ''
L = ''
i = 0
while NKTL[i] != ' ':
N = N + NKTL[i]
i = i+1
i = i+1
while NKTL[i] != ' ':
K = K + NKTL[i]
i = i+1
i = i+1
while NKTL[i] != ' ':
T = T + NKTL[i]
i = i+1
i = i+1
L = NKTL [i:]
N1 = int (N)
K1 = int(K)
T1 = int (T)
L1 = int(L)
c= N1/T1
if K1%c-L1<0:
print(K1)
else:
if K1%c-L1>(T1 - L1)//2:
print(K1//c+ T1+1)
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