#include <bits/stdc++.h>
using namespace std;

#define ALL(v) v.begin(), v.end()
#define V vector
#define P pair
using ll = long long;


int main() {
    int n; cin >> n;

    V<ll> a(n);
    for(int i = 0; i < n; i++) cin >> a[i];
    sort(ALL(a));

    int ans = 1;
    ll pre = a[0];
    for(int i = 1; i < n; i++){
        if(pre + 1 < a[i]){
            pre = a[i];
        }else{
            pre = a[i];
            ans++;
        }
    }
    cout << ans << endl;


    return 0;
}