#include <bits/stdc++.h>

//#include <atcoder/all>
#define For(i, a, b) for (int(i) = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int(i) = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

constexpr lint mod = 1000000007;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

int main() {
    int n;
    scanf("%d", &n);
    lint a[n], dp[n];
    map<lint, int> mp;
    memset(dp, 0, sizeof(dp));
    rep(i, n) scanf("%lld", &a[i]);
    sort(a, a + n);
    rep(i, n) mp[a[i]] = i;
    rrep(i, n) if (dp[i] == 0) {
        dp[i] = 1;
        int t = a[i] - 2;
        while (t > 0 && mp.find(t) != mp.end()) {
            dp[mp[t]] = dp[mp[t + 2]] + 1;
            t -= 2;
        }
    }
    lint ans = n;
    rep(i, n - 1) if (a[i] + 1 == a[i + 1]) ans += dp[i + 1];
    printf("%lld\n", ans);
}