#include <bits/stdc++.h>
using namespace std;
int G[100001];
int X[1000];
int main(int argc, char* argv[]) {
  int r, a, i, j, p, t, m, n, c, v;
  cin >> n;
  for (i = 1; i <= n; i++) {
    t = 2 * i;
    c = 0;
    p = sqrt((double)(t + 1));
    v = -1;
    for (m = 2; m <= p; m++)
      if (t % m == 0 && (t / m - m + 1) % 2 == 0) {
        a = (t / m - m + 1) / 2;
        if (a > 0) {
          r = 0;
          for (j = 0; j < m; j++) r = r ^ G[a + j];
          X[c++] = r;
          if (r == 0 && v == -1) v = m;
        }
      }
    sort(X, X + c);
    r = 0;
    for (j = 0; j < c && X[j] <= r; j++)
      if (X[j] == r) r++;
    G[i] = r;
  }
  cout << v;
  return 0;
}
