#include <bits/stdc++.h>
using namespace std;
const int dr[] = {1, 0, -1, 0, 1, 1, -1, -1};
const int dc[] = {0, 1, 0, -1, 1, -1, -1, 1};
const double eps = 1e-9;
const int INF = 0x7FFFFFFF;
const long long INFLL = 0x7FFFFFFFFFFFFFFFLL;
const double pi = acos(-1);
template <class T>
T take(queue<T> &O) {
  T tmp = O.front();
  O.pop();
  return tmp;
}
template <class T>
T take(stack<T> &O) {
  T tmp = O.top();
  O.pop();
  return tmp;
}
template <class T>
T take(priority_queue<T> &O) {
  T tmp = O.top();
  O.pop();
  return tmp;
}
template <class T>
inline void getint(T &num) {
  bool neg = 0;
  num = 0;
  char c;
  while ((c = getchar_unlocked()) && (!isdigit(c) && c != '-'))
    ;
  if (c == '-') {
    neg = 1;
    c = getchar_unlocked();
  }
  do num = num * 10 + c - '0';
  while ((c = getchar_unlocked()) && isdigit(c));
  if (neg) num = -num;
}
template <class T>
inline bool inRange(T z, T a, T b) {
  return a <= z && z <= b;
}
void OPEN(string in = "input.txt", string out = "output.txt") {
  freopen(in.c_str(), "r", stdin);
  freopen(out.c_str(), "w", stdout);
  return;
}
int arr[200005], s, n;
int ans, hitung[200005], bolong[200005];
int main(int argc, char **argv) {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> s;
  --s;
  for (int(i) = (0), _t = (n); i < (_t); ++(i)) cin >> arr[i];
  int offsetans = 0;
  if (arr[s] != 0) ++offsetans, arr[s] = 0;
  if (n == 1) {
    cout << offsetans << "\n";
    return 0;
  }
  sort(arr, arr + (n));
  for (int(i) = (1), _t = (n); i < (_t); ++(i))
    ++hitung[arr[i]], bolong[arr[i]] |= 1;
  for (int(i) = (1), _t = (n); i <= (_t); ++(i))
    hitung[i] += hitung[i - 1], bolong[i] += bolong[i - 1];
  ans = INF;
  for (int(tertinggi) = (1), _t = (n - 1); tertinggi <= (_t); ++(tertinggi)) {
    int berlebih = hitung[n] - hitung[tertinggi] + hitung[0];
    int kurang = tertinggi - (bolong[tertinggi] - bolong[0]);
    int jawaban = max(berlebih, kurang);
    ans = min(ans, jawaban);
  }
  cout << ans + offsetans << "\n";
}
