#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
mt19937 ggen;
int n, s;
int a[200010];
int ctr[200010];
vector<int> v;
void solve() {
  cin >> n >> s;
  s--;
  for (int i = 0; i < n; i++) cin >> a[i];
  int ans = 0;
  if (a[s] != 0) ans++;
  for (int i = 0; i < n; i++) {
    if (i != s) {
      if (a[i] == 0) a[i] = 200009;
      ctr[a[i]]++;
      v.push_back(a[i]);
    }
  }
  sort(v.begin(), v.end());
  for (int i = 1; !v.empty() && i <= v.back(); i++) {
    if (ctr[i] == 0) {
      ans++;
      ctr[v.back()]--;
      v.pop_back();
    }
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  ggen = mt19937(13);
  solve();
  return 0;
}
