#include <bits/stdc++.h>
using namespace std;
#define f(i,k,n) for(ll i=k; i<n; i++)
#define ll long long
const int inf = INT_MAX;

void solve()
{
    ll n,k;
    cin>>n>>k;
    ll a[k];
    set<ll> s;
    f(i,0,k)
    {    
        cin>>a[i];
        s.insert(a[i]);
    }
    int cnt=-1;
    f(i,0,n)
    {
        if(s.find(a[i])!=s.end())
        {
            s.insert(a[i]);
            if(s.begin()!=s.lower_bound(a[i]))
            {
                cnt++;
                s.erase(s.begin(),s.lower_bound(a[i]));
            }
        }
    }
    cout<<cnt<<"\n";
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1;
    //cin>>t;
    while(t--)  solve();
    return 0;
}