n, k=map(int, input().split())
def solve(x):
    if x<=k:
        return x
    y=solve(x-(x+k-1)//k)
    q=y//(k-1)
    r=y%(k-1)
    if r==0:
        return q*k
    else:
        return q*k+1+r
print(solve(n))