479E

#include <bits/stdc++.h>
#define MAX 5007
#define INF 1000000007

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

ll dp[MAX][MAX], sum[MAX];
int limite, n, k;
int main(){
    memset(dp, -1, sizeof dp);
    int a;cin >> n >> a >> limite >> k;

    for(int i = 1; i <= n; i++) dp[0][i] = 1;
    dp[0][limite] = 0;
    for(int i = 1; i <= k; i++){
        for(int j = 1; j <= n; j++) sum[j] = (sum[j-1] + dp[i-1][j])%INF;

        for(int j = 1; j <= n; j++){

            if(j == limite) continue;
            int dif = abs(j-limite);
            if(j > limite) dp[i][j] = (sum[min(j+dif-1, n)]-sum[limite] + INF)%INF;
            else if(j < limite) dp[i][j] = (sum[limite-1]-sum[max(j-dif, 0)] + INF)%INF;
            dp[i][j] = (dp[i][j]-dp[i-1][j]+INF)%INF;
        }
    }

    //for(int i = 0; i <= k; i++){
    //  for(int j = 1; j <= n; j++) cout << dp[i][k] << " ";
    //  cout << endl;
    //}
    cout << dp[k][a]<< endl;
    return 0;
}