#include "testlib.h"
#include<bits/stdc++.h>
using namespace std;

int main(){
	registerValidation();
	int n = inf.readInt(1,33,"n");
	inf.readEoln();
	vector<int> ar(n);
	for (int i = 0; i < n ; i++){
	    int c = inf.readInt(3,35,"c");
	    ar[i] = c;
	    if (i == n-1) inf.readEoln();
	    else inf.readSpace();
	}
	sort(ar.begin(),ar.end());
	int ans = ar[0];
	for (int i = 1; i < n; i++){
	    assert(ar[i-1] < ar[i]);
	    if (ar[i-1] + 1 != ar[i]) ans += ar[i];
	}
	cout << ans << endl;
	inf.readEof();
	return 0;
}