#include<bits/stdc++.h>
#define int long long
using namespace std;
int L,n,k,a[100005],ma,ans;
bool chk(int x){
	int cnt=0;
	for(int i=2;i<=n;i++)
		if(a[i]-a[i-1]>x)
			cnt+=ceil((a[i]-a[i-1])*1.0/x)-1;
	return cnt<=k;
}
signed main(){
	cin>>L>>n>>k;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		ma=max(ma,a[i]-a[i-1]);
	}	
	int l=0,r=ma,mid;
	while(l<=r){
		mid=(l+r)/2;
		if(chk(mid)){
			ans=mid;
			r=mid-1;
		}
		else l=mid+1;
	}
	cout<<ans;
	return 0;
}