#include <bits/stdc++.h>
using namespace std;
const int N = 5100, M = 1000000007;
int i, j, k, l, m, n, o, p, f[4][N], g[N], a, b, d;
inline int Solve() {
  f[0][a] = 1;
  int i, y, cul, now, last;
  for (i = 1; i <= k; i++) {
    now = i & 1;
    last = now ^ 1;
    g[0] = 0;
    for (j = 1; j <= n; j++) {
      g[j] = g[j - 1] + f[last][j];
      if (g[j] >= M) g[j] -= M;
    }
    for (y = 1; y <= d - 1; y++) {
      o = (d - 1 + y) >> 1;
      f[now][y] = g[o];
      if (o >= y) {
        f[now][y] -= f[last][y];
        if (f[now][y] < 0) f[now][y] += M;
      }
    }
    f[now][d] = 0;
    for (y = d + 1; y <= n; y++) {
      o = (d + 1 + y) >> 1;
      if ((o << 1) < (d + 1 + y)) o++;
      if (o <= n) {
        f[now][y] = g[n] - g[o - 1];
        if (f[now][y] < 0) f[now][y] += M;
      } else
        f[now][y] = 0;
      if (o <= y) {
        f[now][y] -= f[last][y];
        if (f[now][y] < 0) f[now][y] += M;
      }
    }
  }
  int ans = 0;
  now = k & 1;
  for (i = 1; i <= n; i++) {
    ans += f[now][i];
    if (ans >= M) ans -= M;
  }
  return ans;
}
int main() {
  cin >> n >> a >> d >> k;
  cout << Solve() << endl;
  return 0;
}
