prison

There are an infinite number of prisoners. Initially, the prisoners are numbered 0, 1, 2, ....

Do the following N times:

* Release the 0th prisoner and execute the k, 2k, 3k, ... th prisoners.
* Then renumber the remaining prisoners. At this time, the prisoners with the smallest original numbers are numbered 0, 1, 2, ... in order.



Find the number that was originally assigned to the prisoner released in the Nth operation.

Constraints

* 1 ≤ N ≤ 10 ^ 5
* 2 ≤ k ≤ 10 ^ 5
* The answer is less than 10 ^ {18}.



Input Format

Input is given from standard input in the following format.


N k


Output Format

Print the answer in one line.

Sample Input 1


4 2


Sample Output 1


7


Sample Input 2


13


Sample Output 2


0


Sample Input 3


100000 100000


Sample Output 3


99999






Example

Input

4 2


Output

7
#include <bits/stdc++.h>
//typedef
//-------------------------#include <bits/stdc++.h>

const double pi = 3.141592653589793238462643383279;

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s)
{
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T>
inline string toString(T x)
{
  ostringstream sout;
  sout << x;
  return sout.str();
}
inline int readInt()
{
  int x;
  scanf("%d", &x);
  return x;
}

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<long long, long long> PLL;
typedef pair<int, PII> TIII;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;

//container util

//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SQ(a) ((a) * (a))
#define EACH(i, c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

//repetition
//------------------------------------------
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define MOD 1000000007

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto &a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
const double EPS = 1E-8;

#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)

class UnionFind
{
public:
  vector<int> par;
  vector<int> siz;

  UnionFind(int sz_) : par(sz_), siz(sz_, 1)
  {
    for (ll i = 0; i < sz_; ++i)
      par[i] = i;
  }
  void init(int sz_)
  {
    par.resize(sz_);
    siz.assign(sz_, 1LL);
    for (ll i = 0; i < sz_; ++i)
      par[i] = i;
  }

  int root(int x)
  {
    while (par[x] != x)
    {
      x = par[x] = par[par[x]];
    }
    return x;
  }

  bool merge(int x, int y)
  {
    x = root(x);
    y = root(y);
    if (x == y)
      return false;
    if (siz[x] < siz[y])
      swap(x, y);
    siz[x] += siz[y];
    par[y] = x;
    return true;
  }

  bool issame(int x, int y)
  {
    return root(x) == root(y);
  }

  int size(int x)
  {
    return siz[root(x)];
  }
};

ll modPow(ll x, ll n, ll mod = MOD)
{
  ll res = 1;
  while (n)
  {
    if (n & 1)
      res = (res * x) % mod;

    res %= mod;
    x = x * x % mod;
    n >>= 1;
  }
  return res;
}

#define SIEVE_SIZE 5000000 + 10
bool sieve[SIEVE_SIZE];
void makeSieve()
{
  for (int i = 0; i < SIEVE_SIZE; ++i)
    sieve[i] = true;
  sieve[0] = sieve[1] = false;
  for (int i = 2; i * i < SIEVE_SIZE; ++i)
    if (sieve[i])
      for (int j = 2; i * j < SIEVE_SIZE; ++j)
        sieve[i * j] = false;
}

bool isprime(ll n)
{
  if (n == 0 || n == 1)
    return false;
  for (ll i = 2; i * i <= n; ++i)
    if (n % i == 0)
      return false;
  return true;
}

const int MAX = 2000010;
long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit()
{
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++)
  {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}

// 二項係数計算
long long COM(int n, int k)
{
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

long long extGCD(long long a, long long b, long long &x, long long &y)
{
  if (b == 0)
  {
    x = 1;
    y = 0;
    return a;
  }
  long long d = extGCD(b, a % b, y, x);
  y -= a / b * x;
  return d;
}
// 負の数にも対応した mod (a = -11 とかでも OK)
inline long long mod(long long a, long long m)
{
  return (a % m + m) % m;
}

// 逆元計算 (ここでは a と m が互いに素であることが必要)
long long modinv(long long a, long long m)
{
  long long x, y;
  extGCD(a, m, x, y);
  return mod(x, m); // 気持ち的には x % m だが、x が負かもしれないので
}
ll GCD(ll a, ll b)
{

  if (b == 0)
    return a;
  return GCD(b, a % b);
}

typedef vector<ll> vec;
typedef vector<vec> mat;

mat mul(mat &A, mat &B)
{
  mat C(A.size(), vec((int)B[0].size()));
  for (int i = 0; i < A.size(); ++i)
  {
    for (int k = 0; k < B.size(); ++k)
    {
      for (int j = 0; j < B[0].size(); ++j)
      {
        C[i][j] = (C[i][j] + A[i][k] * B[k][j] % MOD) % MOD;
      }
    }
  }
  return C;
}
mat matPow(mat A, ll n)
{
  mat B(A.size(), vec((int)A.size()));

  for (int i = 0; i < A.size(); ++i)
  {
    B[i][i] = 1;
  }

  while (n > 0)
  {
    if (n & 1)
      B = mul(B, A);
    A = mul(A, A);
    n >>= 1;
  }
  return B;
}

int main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);

  ll N, k;
  cin >> N >> k;

  ll pos = 0;
  for (int i = 0; i < N - 1; i++)
  {
    pos += pos / (k - 1) + 1;
  }
  cout << pos << endl;

  return 0;
}

