# coding:utf-8

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

haruka_K = K
yuu_k = K

decrease = haruka_K + yuu_k
cnt = 0
nokori_L = L
while True:
    nokori_L -= decrease
    if nokori_L <= decrease:
        break
    else:
        cnt += 1
        continue
yuu_eat = K * cnt

print(yuu_eat)