#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n,b; long long k; //ifstream f("szamok.txt");
    cin>>n>>k>>b; vector<int>a(n);
    for(int i=0; i<n; i++)cin>>a[i];
    sort(a.begin(),a.end());
    for(int i=0; i<k; i++){
        a[b]++;
        int t=b;
        while(a[t]>a[t+1]){
            swap(a[t],a[t+1]);
            t++;}}
    long long s=1; int mod=1000000007;
    for(int i=0; i<n; i++)s=(s*a[i])%mod;
    if(a[b]>0)cout<<s;
    else cout<<-1;
    //cout<<-1;
    /*long long s=0,t=b;
    while(k>s+(a[t]-a[t-1])*(t-b) && t<n){
        s+=(a[t]-a[t-1])*(t-b);
        t++;}
    for(int i=b; i<t; i++)a[i]=a[t-1];
    k-=s;
    for(int i=b; i<t; i++)a[i]+=k/(t-b);
    k=k%(t-b);
    for(int i=b; i<b+k; i++)a[i]++;
    s=1; int mod=1000000007;
    for(int i=0; i<n; i++)s=(s*a[i])%mod;
    if(a[b]>=0)cout<<s;
    else cout<<-1;*/
    //cout<<-1;
    return 0;
}