#include<bits/stdc++.h> using namespace std; const int N=1e5+10; int l,n,m,i,a[N],b[N]; int check(int mid){ int s=0; for(i=2;i<=n;i++){ int p=a[i]-a[i-1]; if(p>mid){ int num=(p-1)/mid; s+=num; } if(s>m){ return s; } } return s; } int main(){ cin>>l>>n>>m; for(i=1;i<=n;i++){ cin>>a[i]; } sort(a+1,a+n+1); int left=1,right=l,mid; while(left<=right){ mid=left+(right-left)/2; if(check(mid)>m){ left=mid+1; }else{ right=mid-1; } } cout<<left; }