#include <bits/stdc++.h>
//#define int long long
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define sc second
#define endl "\n"
#define pii pair<int,int>
using namespace std;
const int MAXN = 1e6+5;
const int mod7 = 1e9+7;
const long long inf = 1e18;
int cnt[MAXN];
int niz[MAXN];
signed main()
{
ios_base::sync_with_stdio(false),cin.tie(0), cout.tie(0);
int tt=1;
//cin >> tt;
while(tt--)
{
int n;
cin >> n;
for(int i=0; i<n; i++)cin >> niz[i];
for(int i=0; i<n; i++)
{
cnt[niz[i]]++;
if(cnt[niz[i]+1] >0)
{
niz[i] = 0;
cnt[niz[i]+1]--;
}
}
int rez = 0;
for(int i=0; i<n; i++)if(niz[i] != 0)rez++;
cout << rez << endl;
}
}
