#include <bits/stdc++.h>

typedef long long ll;
typedef unsigned long long ull;
#define FOR(i, a, b) for (int i = a; i <= b; ++i)
#define ROF(i, a, b) for (int i = a; i >= b; --i)

inline int read() {
    int f = 1, x = 0;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') {
        x = (x << 1) + (x << 3) + (ch ^ 48);
        ch = getchar();
    }
    return x * f;
}

using namespace std;

const int N = 2e6 + 7, mod = 1e9 + 7;
ll ksm(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b & 1) res = res * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return res;
}
int n, d[N], dd[N];
ll L, x[N];
ll pw[N], res;
ll qsum(int l, int r) {
    if (l <= r) return pw[r - l];
    return pw[r + n - l];
}
int buc[20], cm, z[20];
ll qs(vector<pair<int, int>> &hv, int a, int b) {
    int sum = 0;
    cm = 0;
    buc[++cm] = 0, buc[++cm] = n;
    for (auto &t : hv) {
        buc[++cm] = t.first - 1, buc[++cm] = t.second;
    }
    sort(buc + 1, buc + cm + 1);
    cm = unique(buc + 1, buc + cm + 1) - buc - 1;
    FOR(i, 1, cm) z[i] = 0;
    for (auto &t : hv) {
        int l = t.first, r = t.second;
        FOR(i, 1, cm) {
            if (l <= buc[i] && buc[i] <= r) {
                ++z[i];
            }
        }
    }
    FOR(i, 2, cm) {
        if (z[i] == 0) return 0;
        if (z[i] == 2) sum += buc[i] - buc[i - 1] - (buc[i - 1] < a && a <= buc[i]) - (buc[i - 1] < b && b <= buc[i]);
    }
    return pw[sum];
}
ll qsum(int l, int r, int L, int R, int a, int b) {  // l < L
    vector<pair<int, int>> hv;
    if (l <= r) {
        hv.push_back({l, r});
    } else {
        hv.push_back({l, n}), hv.push_back({1, r});
    }
    if (L <= R) {
        hv.push_back({L, R});
    } else {
        hv.push_back({L, n}), hv.push_back({1, R});
    }
    return qs(hv, a, b);
}
ll solve1() {
    ll res = 1;
    FOR(i, 1, n) { res = (res + qsum(i, d[i])) % mod; }
    return res * 2 % mod;
}
ll solve2() {
    ll res = 0;
    FOR(i, 1, n) {
        int p = (i - 1 < 1 ? n : i - 1), q = (d[i] + 1 > n ? 1 : d[i] + 1);
        res = (res + qsum(i, d[i], dd[p], p, i, p) + qsum(i, d[i], q, d[q], i, q) - 1 + mod) % mod;
    }
    return res;
}
void check() {
    FOR(i, 1, n - 1) {
        if ((x[i + 1] - x[i]) * 2 >= L) {
            puts("0");
            exit(0);
        }
    }
    if ((x[1] + L - x[n]) * 2 >= L) {
        puts("0");
        exit(0);
    }
}
int main() {
    // freopen("c.in", "r", stdin);
    // freopen("c.out", "w", stdout);
    n = read(), L = read();
    FOR(i, 1, n) x[i] = read();
    check();
    FOR(i, 1, n) x[n + i] = x[i] + L;
    pw[0] = 1;
    FOR(i, 1, n) pw[i] = pw[i - 1] * 2 % mod;
    for (int i = 1, j = 1; i <= n; ++i) {
        while (j < n * 2 && (x[j + 1] - x[i]) * 2 < L) ++j;
        d[i] = j > n ? j - n : j;
        dd[i] = j + 1;
        if ((x[j + 1] - x[i]) * 2 == L) ++dd[i];
        if (dd[i] > n) dd[i] -= n;
    }
    res = (pw[n] - solve1() + solve2() + mod) % mod;
    // printf("%lld\n", res);
    printf("%lld\n", res * ksm(pw[n], mod - 2) % mod);
    return 0;
}