#include <bits/stdc++.h>
#define Sayan ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define ll long long
#define file(s) if (fopen(s".in", "r")) freopen(s".in", "r", stdin), freopen(s".out", "w", stdout)
#define sz() size()
#define F first
#define S second
#define pb push_back
#define yes cout << "YES\n"
#define no cout << "NO\n"
using namespace std ;
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1};
const ll N = 2e5+5;
const ll inf = 1e18;
const int mod = 1e9+7; // 998244353;
//////////////////////////////////////////////////////
ll TEST=0;
ll a[N];
map<ll,ll>mp;
//////////////////////////////////////////////////////
struct delai{
// ll l,r;
};
//////////////////////////////////////////////////////
void solve(){
ll n;
cin>>n;
for(ll i=1;i<=n;i++){
cin>>a[i];
}
ll ans=0;
for(ll i=n;i>=1;i--){
mp[a[i]]++;
if(mp[a[i]-1]==0)ans++;
else mp[a[i]-1]--;
}
cout<<ans<<"\n";
}
signed main () {
Sayan;
ll t=1;
if(TEST){
cin>>t;
}
while(t--)solve();
}
