#include #include #include #include #include #define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define FOR(i,m,n) for(int i=(m);i<(n);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() const int INF = 0x3f3f3f3f; const long long LINF = 0x3f3f3f3f3f3f3f3fLL; const double EPS = 1e-8; const int MOD = 1000000007; // 998244353; const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1}; struct IOSetup { IOSetup() { cin.tie(nullptr); ios_base::sync_with_stdio(false); cout << fixed << setprecision(20); cerr << fixed << setprecision(10); } } iosetup; /*-------------------------------------------------*/ int mod = MOD; struct ModInt { unsigned val; ModInt(): val(0) {} ModInt(long long x) : val(x >= 0 ? x % mod : x % mod + mod) {} ModInt pow(long long exponent) { ModInt tmp = *this, res = 1; while (exponent > 0) { if (exponent & 1) res *= tmp; tmp *= tmp; exponent >>= 1; } return res; } ModInt &operator+=(const ModInt &rhs) { if((val += rhs.val) >= mod) val -= mod; return *this; } ModInt &operator-=(const ModInt &rhs) { if((val += mod - rhs.val) >= mod) val -= mod; return *this; } ModInt &operator*=(const ModInt &rhs) { val = static_cast(val) * rhs.val % mod; return *this; } ModInt &operator/=(const ModInt &rhs) { return *this *= rhs.inv(); } bool operator==(const ModInt &rhs) const { return val == rhs.val; } bool operator!=(const ModInt &rhs) const { return val != rhs.val; } bool operator<(const ModInt &rhs) const { return val < rhs.val; } bool operator<=(const ModInt &rhs) const { return val <= rhs.val; } bool operator>(const ModInt &rhs) const { return val > rhs.val; } bool operator>=(const ModInt &rhs) const { return val >= rhs.val; } ModInt operator-() const { return ModInt(val ? mod - val : 0); } ModInt operator+(const ModInt &rhs) const { return ModInt(*this) += rhs; } ModInt operator-(const ModInt &rhs) const { return ModInt(*this) -= rhs; } ModInt operator*(const ModInt &rhs) const { return ModInt(*this) *= rhs; } ModInt operator/(const ModInt &rhs) const { return ModInt(*this) /= rhs; } friend ostream &operator<<(ostream &os, const ModInt &rhs) { return os << rhs.val; } friend istream &operator>>(istream &is, ModInt &rhs) { long long x; is >> x; rhs = ModInt(x); return is; } private: ModInt inv() const { // if (__gcd(val, mod) != 1) assert(false); unsigned a = val, b = mod; int x = 1, y = 0; while (b) { unsigned tmp = a / b; swap(a -= tmp * b, b); swap(x -= tmp * y, y); } return ModInt(x); } }; int abs(const ModInt &x) { return x.val; } struct Combinatorics { int val; vector fact, fact_inv, inv; Combinatorics(int val = 10000000) : val(val), fact(val + 1), fact_inv(val + 1), inv(val + 1) { fact[0] = 1; FOR(i, 1, val + 1) fact[i] = fact[i - 1] * i; fact_inv[val] = ModInt(1) / fact[val]; for (int i = val; i > 0; --i) fact_inv[i - 1] = fact_inv[i] * i; FOR(i, 1, val + 1) inv[i] = fact[i - 1] * fact_inv[i]; } ModInt nCk(int n, int k) { if (n < 0 || n < k || k < 0) return ModInt(0); // assert(n <= val && k <= val); return fact[n] * fact_inv[k] * fact_inv[n - k]; } ModInt nPk(int n, int k) { if (n < 0 || n < k || k < 0) return ModInt(0); // assert(n <= val); return fact[n] * fact_inv[n - k]; } ModInt nHk(int n, int k) { if (n < 0 || k < 0) return ModInt(0); return (k == 0 ? ModInt(1) : nCk(n + k - 1, k)); } }; int main() { vector left{-1, 1}, right{-1, 1}; FOR(i, 2, 21) { left.emplace_back(left.back() * 2); right.emplace_back(left.back() * 2 - 1); } int d, l, r, k; cin >> d >> l >> r >> k; int dep_l, dep_r; for (dep_l = 1; dep_l <= d; ++dep_l) { if (left[dep_l] <= l && l <= right[dep_l]) break; } for (dep_r = 1; dep_r <= d; ++dep_r) { if (left[dep_r] <= r && r <= right[dep_r]) break; } // cout << dep_l << ' ' << dep_r << '\n'; Combinatorics com(1 << d); ModInt ans = 0; for (int middle = dep_l; middle >= 1; --middle) { if (dep_r - dep_l + 2 * (dep_l - middle) != k) continue; ans = ModInt(1 << (dep_r - dep_l)) * ModInt(1 << max(dep_l - middle - 1, 0)); if (dep_l == dep_r) { ans *= 1 << (dep_l - 1); ans *= com.fact[(1 << (dep_r - 1)) - 2]; } else { ans *= com.fact[(1 << (dep_r - 1)) - 1]; } break; } for (int i = 1; i <= d; ++i) if (i != dep_r) { ans *= com.fact[1 << (i - 1)]; } cout << ans << '\n'; return 0; }