#include <bits/stdc++.h>
using namespace std;
inline int readChar();
template <class T = int>
inline T readInt();
template <class T>
inline void writeInt(T x, char end = 0);
inline void writeChar(int x);
inline void writeWord(const char *s);
static const int buf_size = 4096;
inline int getChar() {
  static char buf[buf_size];
  static int len = 0, pos = 0;
  if (pos == len) pos = 0, len = fread(buf, 1, buf_size, stdin);
  if (pos == len) return -1;
  return buf[pos++];
}
inline int readChar() {
  int c = getChar();
  while (c <= 32) c = getChar();
  return c;
}
template <class T>
inline T readInt() {
  int s = 1, c = readChar();
  T x = 0;
  if (c == '-') s = -1, c = getChar();
  while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = getChar();
  return s == 1 ? x : -x;
}
static int write_pos = 0;
static char write_buf[buf_size];
inline void writeChar(int x) {
  if (write_pos == buf_size)
    fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
  write_buf[write_pos++] = x;
}
template <class T>
inline void writeInt(T x, char end) {
  if (x < 0) writeChar('-'), x = -x;
  char s[24];
  int n = 0;
  while (x || !n) s[n++] = '0' + x % 10, x /= 10;
  while (n--) writeChar(s[n]);
  if (end) writeChar(end);
}
inline void writeWord(const char *s) {
  while (*s) writeChar(*s++);
}
struct Flusher {
  ~Flusher() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
  }
} flusher;
class TimeTracker {
  clock_t start, end;

 public:
  TimeTracker() { start = clock(); }
  ~TimeTracker() {
    end = clock();
    fprintf(stderr, "%.3lf s\n", (double)(end - start) / CLOCKS_PER_SEC);
  }
};
int a[200007];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n = readInt(), s = readInt(), ans{};
  for (int i = 1; i <= n; i++) {
    int tmp = readInt();
    if (i == s) {
      if (tmp != 0) ans++;
    } else
      a[tmp]++;
  }
  for (int i = 1, j = 1; j < n; i++) {
    if (a[i] != 0)
      j += a[i];
    else
      j++, ans++;
  }
  writeInt(ans, '\n');
}
