#include<bits/stdc++.h>
using namespace std;
struct node{
	int lth,num,lst;
	friend bool operator < (node a,node b){
		return a.lst<b.lst;
	}
}z,z1;
priority_queue<node> q; 
int l,n,k,ans,a[100005];
int main(){
	scanf("%d%d%d",&l,&n,&k);
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}
	for(int i=2;i<=n;i++){
		z.lst=a[i]-a[i-1];
		z.lth=a[i]-a[i-1];
		z.num=1; 
		q.push(z);
	}
	for(int i=1;i<=k;i++){
		z1=q.top();
		q.pop();
		int aa=z1.lst;
		int bb=z1.lth;
		int cc=z1.num;
		cc++;
		aa=(bb+cc-1)/cc;
		z.lst=aa;
		z.lth=bb;
		z.num=cc;
		q.push(z);
	}
	z1=q.top();
	cout<<z1.lst;
	return 0;
}