#include<bits/stdc++.h> using namespace std; const int N=1e6+10; const int INF=0x3f3f3f3f; int ans,l,r,L,n,k,a[N]; bool check(int mid){ int sum=0; for(int i=2;i<=n;++i) sum+=(a[i]-a[i-1]-1)/mid; return sum<=k;
} int main(){ cin>>L>>n>>k; for(int i=1;i<=n;++i) cin>>a[i]; sort(a+1,a+n+1); r=a[n]-1; while(l<r){ int mid=(l+r)/2; if(check(mid)){ r=mid; } else l=mid+1; } cout<<r; return 0; }