#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>
#include<map>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;

signed main(){
	cout<<fixed<<setprecision(10);
	
	int N;
    vector<int> A;
    map<int,int> mp, mp2;
    int con = 0;
    
    cin>>N;
	
    // A.resize(N);
    
	for(int i = 0; i < N; i++){
        int a;
        cin>>a;
        
        mp[a] = 1;
        mp2[a] = 1;
        
        A.push_back(a);
        A.push_back(a+1);
    }
    
    sort(A.begin(), A.end());
    A.erase(unique(A.begin(), A.end()), A.end());
    
    for(int i = 0; i < A.size(); i++){
        if(mp2[A[i]-1]) mp[A[i]] += mp[A[i]-2];
        
        con += mp[A[i]];
    }
    
    cout<<con<<endl;
    
	return 0;
}