#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef long long ll;

int n;
ll a[200000];

void input(){
    cin >> n;
    for(int i = 0; i < n; i++) cin >> a[i];
}


void solve(){
    sort(a, a+n);
    ll ans = 0;
    int cnt = 0;
    vector<ll> dp;
    dp.push_back(1);
    for(int i = 1; i < n; i++){
        int sz = dp.size();
        if(a[i-1]+1 == a[i]){
            if(sz <= 1) dp.push_back(1);
            else dp.push_back(dp[sz-2]+1);
        }else if(a[i-1]+2 == a[i]){
            if(sz == 1) {
                ans += dp[0];
                dp.clear();
                dp.push_back(1);
            }else if(sz >= 2){
                dp.push_back(dp[sz-2]);
                dp.push_back(1);
            }
        }else{
            for(ll x : dp) ans += x;
            if(dp.size() >= 2) ans += dp[sz-2];
            dp.clear();
            dp.push_back(1);
        }
    }
    // cout << ans << endl;
    // for(ll x : dp) cout << x << ' ';
    // cout << endl;
    for(ll x : dp) ans += x;
    if(dp.size() >= 2) ans += dp[dp.size()-2];
    cout << ans << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    input();
    solve();
}