#include <bits/stdc++.h>
using namespace std;
template <class T>
void rd(T &x) {
  x = 0;
  int f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9')
    x = (x << 3) + (x << 1) + ch - '0', ch = getchar();
  x *= f;
}
const long long inf = 1e16;
const int maxn = 505;
int n;
long long f[maxn][maxn];
int nxt(int a, int b) {
  int c = a + b;
  if (c > n)
    return c % n;
  else
    return c;
}
long long dfs(int l, int r) {
  if (nxt(l, 1) == r) return 0;
  if (f[l][r]) return f[l][r];
  if (nxt(l, 2) == r) return l * nxt(l, 1) * nxt(l, 2);
  long long res = inf;
  int u = nxt(l, 1);
  while (u != r) {
    res = min(res, l * r * u + dfs(l, u) + dfs(u, r));
    u = nxt(u, 1);
  }
  return f[l][r] = res;
}
int main() {
  rd(n);
  printf("%lld\n", dfs(1, n));
  return 0;
}
