#include <bits/stdc++.h> using namespace std; int l,n,m,a[100005],lb,ub; bool check(int x) { int p = a[0],sum = 0; for(int i = 1; i <= n+1; i++) { if(a[i]-p<x) { sum++; } else { p = a[i]; } } return sum<=m; } int main() { cin >> l >> n >> m; for(int i = 1; i <= n; i++)cin>>a[i]; a[n+1] = l; ub = l+1; while(ub-lb>1) { int mid = (ub+lb)/2.0; if(check(mid)) lb=mid; else ub=mid; } cout << lb; }