#include <bits/stdc++.h>
using namespace std;

#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define orange(a...) orange_(#a, a)
#define debug(a...) debug_(#a, a)
template <typename i>
void orange_(const char * s, i l, i r) {
    cerr << "\e[1;32m[ " << s << " ] = [ ";
    for (int f = 0; l != r; l++)
        cerr << (f++ ? " " : "") << *l;
    cerr << " ]\e[0m\n";
}
template <typename ...T>
void debug_(const char * s, T ...a) {
    cerr << "\e[1;32m(" << s << ") = (";
    int cnt = sizeof...(T);
    (..., (cerr << a << (--cnt ? ", " : ")\e[0m\n")));
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, x;
    cin >> n >> x;
    vector<int> a(n);
    for (int &ai : a) {
        cin >> ai;
        ai = min(ai, x - ai);
    }
    deque<int> dq;
    for (int ai : a) {
        if (dq.empty())
            dq.push_back(ai);
        else if (dq.back() == ai)
            dq.pop_back();
        else
            dq.push_back(ai);
    }
    while (dq.size() >= 2) {
        if (dq.front() == dq.back()) {
            dq.pop_front();
            dq.pop_back();
        } else break;
    }
    cout << (n - dq.size()) / 2 << '\n';
    return 0;
}