#include<bits/stdc++.h> using namespace std; int o,n,m,a[114514]; bool check(int x){ int cnt = 0,last = 0; for (int i = 1;i <= n + 1;i++){ if (a[i] - last < x){ cnt++; } else{ last = a[i]; } } return cnt <= m; } int main(){ cin>>o>>n>>m; for (int i = 1;i <= n;i++){ cin>>a[i]; } a[n + 1] = o; int l = 1,r = o + 1; while (l <= r){ int mid = (l + r) / 2; if (check(mid)){ l = mid + 1; } else{ r = mid - 1; } } cout<<r<<endl; return 0; }