#include <bits/stdc++.h>
using namespace std;
long long mod = 1e9 + 7;
long long nop = 100;
vector<int> primes(nop, 1);
void sieve() {
  primes[1] = primes[0] = 0;
  for (long long i = 2; i * i <= nop; i++) {
    if (primes[i]) {
      for (long long j = i * i; j <= nop; j += i) {
        primes[j] = 0;
      }
    }
  }
}
long long gcd(long long a, long long b) {
  if (b > a) swap(b, a);
  if (b == 0) return a;
  return gcd(b, a % b);
}
void extgcd(long long a, long long b, long long& x, long long& y) {
  if (a == 0) {
    x = a;
    y = b;
    return;
  }
  extgcd(b % a, a, x, y);
  long long y1 = y, x1 = x;
  x = y1 - (b / a) * x1;
  y = x1;
}
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
long long bexp(long long num, long long e) {
  long long ans = 1;
  while (e > 0) {
    if (e & 1) {
      ans *= num;
    }
    num *= num;
    e >>= 1;
  }
  return ans;
}
long long mexp(long long num, long long e) {
  long long ans = 1;
  while (e > 0) {
    if (e & 1) {
      ans = (ans * num) % mod;
    }
    num *= num;
    num %= mod;
    e >>= 1;
  }
  return ans;
}
long long modinv(long long a) { return bexp(a, mod - 2); }
long long n, a, b, k;
int main() {
  cin.tie(0);
  cout.tie(0);
  ios::sync_with_stdio(0);
  cin >> n >> a >> b >> k;
  vector<long long> dp(n + 2, 0), sum(n + 2, 0);
  dp[a] = 1;
  for (long long i = 0; i < k; i++) {
    for (long long j = 1; j <= n; j++) {
      long long t = abs(j - b) - 1, l = max((long long)1, j - t),
                r = min(n, j + t);
      if (t > 0) {
        sum[l] = (sum[l] + dp[j]) % mod;
        sum[r + 1] = (sum[r + 1] - dp[j] + mod) % mod;
        sum[j] = (sum[j] - dp[j] + mod) % mod;
        sum[j + 1] = (sum[j + 1] + dp[j]) % mod;
      }
    }
    for (long long j = 1; j <= n; j++) {
      dp[j] = (dp[j - 1] + sum[j] + mod) % mod;
      sum[j] = 0;
    }
  }
  long long ans = 0;
  for (long long i = 1; i <= n; i++) {
    ans = (ans + dp[i]) % mod;
  }
  cout << ans << endl;
  return 0;
}
