#include<iostream>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#define int long long
#define mod 1000000007
#define for0(i, n) for(int i = 0; i < (n); i++)
#define for1(i, n) for(int i = 1; i <= (n);i++)
#define mp make_pair
using namespace std;
int a, b, c, d, n, ans;
int ar[234567];
string s;
bool b1, b2;
signed main() {
	cin >> n;
	for1(i, n) { cin >> a; ans += a; }
	cout << ans - (n*(n + 1) / 2) << endl;
}
