#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define fo(i,a,b) for(i=a;i<=b;i++)
#define fod(i,a,b) for(i=a;i>=b;i--)
using namespace std;
const int maxn=500007;
int i,j,k,t,n,m,ans,rr,cc,z,y,mid,x;
int l[maxn],r[maxn],lt[maxn],rt[maxn],a[maxn],b[maxn],c[maxn];
bool bz;
int main(){
// freopen("fan.in","r",stdin);
scanf("%d%d%d",&n,&rr,&cc);
fo(i,1,n)scanf("%d",&a[i]);
ans=0x7fffffff;
sort(a+1,a+1+n);
fo(i,1,n-cc+1)b[i]=a[i+cc-1]-a[i];fo(i,n-cc+2,n)b[i]=-1;
z=1,y=n-cc+1;
fo(i,z,y)c[++c[0]]=b[i];
sort(c+1,c+1+c[0]);
while(z<y){
mid=(z+y)/2;x=c[mid];
bz=0;
j=1;int sum=0;
while(j<=n-cc+1){
if(a[j+cc-1]-a[j]<=x){
sum++;
j+=cc;
}
else j++;
}
if(sum>=rr)y=mid,ans=min(ans,x);else z=mid+1;
}
printf("%d\n",ans);
}