N, K = map(int, input().split())

if N <= K:
    exit(print(1))

def solve(x): # xダメージで K位以内に入れるか？
    # x ダメージ与えた人数がK人いる
    nokori = N - K*x
    return nokori <= x - 1

ok = N
ng = 0
while abs(ok - ng) != 1:
    mid = (ok + ng)//2
    if solve(mid):
        ok = mid
    else:
        ng = mid

print(ok)