#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#define double long double
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000007
#define PI 3.14159265359
#define MAXN 100005
#define INF 1000000005
#define LINF 1000000000000000005ll
#define CODE_START ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n,a[1000005],ans=0;
map<ll,ll>viz;
int32_t main(){
CODE_START;
cin>>n;
for(ll i=1;i<=n;i++)
{
cin>>a[i];
}
reverse(a+1,a+n+1);
for(ll i=1;i<=n;i++)
{
if(viz[a[i]-1]>=1){
viz[a[i]]++;
viz[a[i]-1]--;
continue;
}
ans++;
viz[a[i]]++;
}
cout<<ans;
}
