Task 14

n, m, k = map(int, input().split())
if m < 2 or k < 2:
    print(0)
else:
    if n % (k-2) != 0 and m//(n/(k-2)+1) >= 2:
        print(n//(k-2)+1)
    elif n % (k-2) == 0 and m - 2 * n // (k - 2) > 0:
        print(n // (k-2) + (m - 2 * n // (k - 2)) // (n // (k-2) + 1))
    elif n % (k-2) == 0 and m//(n//(k-2)) >=2:
        print(n//(k-2))
    else:
        print(0)