#include<bits/stdc++.h> using namespace std; int l,n,m,a[50010]; int check(int mid){ int p=0,cnt=0; for(int i=0;i<n;i++){ if(a[i]-p<mid){ cnt++; } else{ p=a[i]; } } if(l-p<mid){ cnt++; } return cnt; } int main(){ cin>>l>>n>>m; for(int i=0;i<n;i++){ cin>>a[i]; } int left=0,right=l; while(left<=right){ int mid=left+(right-left)/2; if(check(mid)<=m){ left=mid+1; } else{ right=mid-1; } } cout<<right; return 0; }