#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, s;
  cin >> n >> s;
  vector<int> a(n);
  --s;
  for (int i = 0; i < n; ++i) cin >> a[i];
  int ans = 0;
  if (a[s] != 0) {
    a[s] = 0;
    ++ans;
  }
  for (int i = 0; i < n; ++i)
    if ((i != s) && (a[i] == 0)) a[i] = n;
  map<int, int> workers;
  for (int i = 0; i < n; ++i) ++workers[a[i]];
  int count = n - 1;
  int max = n;
  while (!workers.count(max)) --max;
  for (int i = 1; count; ++i) {
    if (workers[i])
      count -= workers[i];
    else {
      ++ans;
      --count;
      --workers[max];
      while (!workers[max]) --max;
    }
  }
  cout << ans;
}
