#define _USE_MATH_DEFIMES
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <climits>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

const int MOD = 1'000'000'007;
const int MOD2 = 998'244'353;
const int INF = 1'000'000'000; //1e9
const int NIL = -1;
const long long LINF = 1'000'000'000'000'000'000; // 1e18
const long double EPS = 1E-10L;

template<class T, class S> inline bool chmax(T &a, const S &b){
    if(a < b){a = b; return true;}
    return false;
}
template<class T, class S> inline bool chmin(T &a, const S &b){
    if(b < a){a = b; return true;}
    return false;
}
template<class T, class Container> inline bool exist(Container &s, const T &e){
    return (s.find(e) != std::end(s));
}
template<class T> inline bool inside(T x, T lx, T rx){
    return (std::clamp(x, lx, rx) == x);
}
template<class T> inline bool inside(T x, T y, T lx, T rx, T ly, T ry){
    return inside(x, lx, rx) && inside(y, ly, ry);
}










int main(){
    int N; std::cin >> N;
    std::vector<int> A(N);
    for(auto &e: A) std::cin >> e;
    std::sort(std::begin(A), std::end(A));
    int ans{A[0]};
    for(int i{1}; i < N; ++i){
        if(A[i] == A[i-1] + 1) ans += A[i];
    }
    std::cout << ans << std::endl;
    return 0;
}