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