#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x;
  cin >> n >> x;
  int a[n];
  for (int i = 0; i < n; i++) cin >> a[i];
  long long power_value = a[n - 1];
  int power_count = 0;
  for (int i = n - 1; i >= 0;) {
    while (i >= 0 && power_value == a[i]) power_count++, i--;
    if (power_count % x != 0) break;
    power_value--;
    power_count /= x;
  }
  while (power_count % x == 0) {
    power_value--;
    power_count /= x;
  }
  if (power_value < 0) power_value = 0;
  long long sum = 0;
  for (int i = n - 1; i >= 0; i--) sum += a[i];
  power_value = sum - power_value;
  long long gcd = 1;
  const int modulo = 1000000007;
  for (long long i = x; power_value > 0; power_value >>= 1) {
    if (power_value & 1) gcd = gcd * i % modulo;
    i = i * i % modulo;
  }
  cout << gcd;
}
