A,B,C,D =map(int,input().split())

if B/C >=A and A+B<=D:
    ans = A
elif B/C < A and B/C>=1 and int(B/C)+B<D:
    ans=B/C
elif B/C < A and B/C>=1 and int(B/C)+B>D:
    ans=D/(C+1)
else:
    ans=0
print(int(ans))