#include <bits/stdc++.h>
using namespace std;
const long long MOD = long long(1e9 + 7);
const long long LLINF = LLONG_MAX;
const int IINF = INT_MAX;
const int MAX_N = int(1e5) + 5;
const double EPS = 1e-8;
int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};
int main() {
  int n, ans = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int a;
    ans += a - 1;
  }
  cout << ans << endl;
  return 0;
}
