#include <iostream>

#include <queue>

#include <algorithm>

#include <vector>

using namespace std;

typedef long long ll;

int tree[100001];

int find(int x) {

if (tree[x] == x) return x;

return tree[x] = find(tree[x]);

}

int main()

{

cin.tie(0) -> sync_with_stdio(0);

int G, P; cin >> G >> P; for (int i = 0; i <= G; i++) tree[i] = i;

int result = 0;

bool full = false;

for (int i = 0; i < P; i++) {

int gi; cin >> gi; if (full) continue;

int found = find(gi);

if (found > 0) {

result++;

tree[found] = found - 1;

} else full = true;

}

cout << result;

return 0;

}