#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <set>
#include <string>
#include <cmath>
#include <map>
#include <iomanip>
#include <tuple>
#define INF 1000000009
#define LINF 1000000000000000009
#define double long double
#define all(a) a.begin(),a.end()
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;
//ll mod = 1000000007;
//ll mod = 998244353;

int main() {
	int n;
	cin >> n;
	vector<ll> a(n);
	ll ans = 0;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		ans += a[i];
		ans -= i;
		ans -= 1;
	}
	cout << ans << endl;
}
