#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    ll n; cin >> n;
    ll a[n] = {};
    rep(i,n) cin >> a[i];
    sort(a, a+n);
    ll ans = 0;
    ll f[n] = {};
    drep(i,n){
        if(i+1<n && a[i+1]==a[i]+2){
            f[i] = f[i+1] + 1;
        }
        if(i+2<n && a[i+2]==a[i]+2){
            f[i] = f[i+2] + 1;
        }
        if(i > 0 && a[i-1]+1==a[i]){
            ans += f[i]+1;
        }
    }
    ans += n;
    cout << ans << endl;
    return 0;
}