#include <iostream>
using namespace std;


int c[100];

int main() {
	int n; cin >> n;
	
	for (int i = 0; i < n; i++) {
		int a; cin >> a;
		c[a]++;
	}
	
	
	
	int cnt = c[0];
	for (int i = 0; i < 90; i++) {
		if (c[i] == 0) {
			cnt += c[i + 1] * (i + 1);
			// if (c[i + 1] != 0) cout << "i: " << i << endl;
		}
	}
	cout << cnt << endl;
	
	return 0;
}