#include <bits/stdc++.h>
using namespace std;
const int maxn = 400010;
const int mod = 1e9 + 7;
const int MAX = 1000000010;
const double eps = 1e-6;
const double PI = acos(-1);
template <typename T>
inline void read(T &x) {
  x = 0;
  T f = 1;
  char ch;
  do {
    ch = getchar();
    if (ch == '-') f = -1;
  } while (ch < '0' || ch > '9');
  do x = x * 10 + ch - '0', ch = getchar();
  while (ch <= '9' && ch >= '0');
  x *= f;
}
template <typename A, typename B>
inline void read(A &x, B &y) {
  read(x);
  read(y);
}
template <typename A, typename B, typename C>
inline void read(A &x, B &y, C &z) {
  read(x);
  read(y);
  read(z);
}
template <typename A, typename B, typename C, typename D>
inline void read(A &x, B &y, C &z, D &w) {
  read(x);
  read(y);
  read(z);
  read(w);
}
template <typename A, typename B>
inline A fexp(A x, B p) {
  A ans = 1;
  for (; p; p >>= 1, x = 1LL * x * x % mod)
    if (p & 1) ans = 1LL * ans * x % mod;
  return ans;
}
template <typename A, typename B>
inline A fexp(A x, B p, A mo) {
  A ans = 1;
  for (; p; p >>= 1, x = 1LL * x * x % mo)
    if (p & 1) ans = 1LL * ans * x % mo;
  return ans;
}
int n, m, ans;
int A[maxn], B[maxn], C[maxn], fail[maxn], Ans[maxn];
void Work() {
  if (n == 1) {
    printf("%d\n", 1);
    printf("%d\n", (A[1] + A[1]) % m);
    return;
  }
  for (int i = (2); i <= (n - 1); i++) {
    int j;
    for (j = fail[i - 1]; j && C[j + 1] != C[i]; j = fail[j])
      ;
    if (C[j + 1] == C[i]) fail[i] = j + 1;
  }
  int now = 0;
  for (int i = (1); i <= (n * 2 - 2); i++) {
    while (now && C[now + 1] != B[i]) now = fail[now];
    if (C[now + 1] == B[i]) now++;
    if (now == n - 1) {
      ans++;
      int t = i - (n - 1) + 1;
      t = (n - t + 1);
      Ans[ans] = (A[1] + A[t]) % m;
    }
  }
  sort(Ans + 1, Ans + ans + 1);
  printf("%d\n", ans);
  for (int i = (1); i <= (ans); i++) printf("%d ", Ans[i]);
  if (ans) puts("");
}
void Init() {
  read(n, m);
  for (int i = (1); i <= (n); i++) read(A[i]);
  for (int i = (n); i >= (2); i--) B[n - i + 1] = A[i] - A[i - 1];
  B[n] = (A[1] - A[n] + m) % m;
  for (int i = (1); i <= (n - 1); i++) B[i + n] = B[i];
  for (int i = (1); i <= (n - 1); i++) C[i] = A[i + 1] - A[i];
}
int main() {
  Init();
  Work();
  return 0;
}
