#include<bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1000000007;
int n,a,b,k;
int dp[5005][5005],pre[5005][5005];
signed main(){
	cin >> n >> a >> b >> k;
	dp[0][a] = 1;
	for(int i = a;i<=n;i++)pre[0][i] = 1;
	for(int i = 1;i<=k;i++){
		for(int j = 1;j<=n;j++){
			if(j<b){
				dp[i][j] = pre[i-1][(j+b-1)>>1]-dp[i-1][j];
			}if(j>b){
				dp[i][j] = pre[i-1][n]-pre[i-1][(j+b)>>1]-dp[i-1][j];
			}dp[i][j]+=mod,dp[i][j]%=mod;
	//		cout << dp[i][j] << " ";
		}for(int j = 1;j<=n;j++)pre[i][j] = (pre[i][j-1]+dp[i][j])%mod;
	//	cout << endl;
	}cout << pre[k][n] << endl;
	return 0;
}