#include //#include #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 pii; typedef pair pll; template bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; } template bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; } template T div_floor(T a, T b) { if (b < 0) a *= -1, b *= -1; return a >= 0 ? a / b : (a + 1) / b - 1; } template 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 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); }