#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000003

int main(){	
	
	int N;
	cin>>N;
	
	vector<long long> A(N);
	rep(i,N){
		cin>>A[i];
	}
	
	sort(A.begin(),A.end());
	
	long long ans = N;
	vector<vector<long long>> X;
	rep(i,N){
		if(i==0)X.push_back(vector<long long>(1,A[i]));
		else{
			if(X.back().back()+1==A[i])X.back().push_back(A[i]);
			else X.push_back(vector<long long>(1,A[i]));
		}
	}
	
	vector<long long> dp(N+100,0);
	
	for(int i=2;i<dp.size();i++){
		dp[i] += dp[i-1];
		dp[i] += (i-2)/2;
	}
	
	rep(i,X.size()){
		if(X[i].size()==0)continue;
		ans += X[i].size()-1;
		ans += dp[X[i].size()];
	}
	
	cout<<ans<<endl;
	
    return 0;
}