```cpp
#include<bits/stdc++.h>
using namespace std;
int L,M,N,a[50005];
int main(){
cin>>L>>N>>M;
for(int i=1;i<=N;i++)
cin>>a[i];
a[N+1]=L;
int left=0,right=L;
while(left<=right){
int mid=(left+right)/2;
int k=0,ans=0;
for(int i=1;i<=N+1;i++){
if(a[i]-a[k]<mid)ans++;
else k=i;
}
if(ans>M)right=mid-1;
else left=mid+1;
}
cout<<left-1;
return 0;
}
```
@[acmwriter](/user/800751) 已AC！
by acmwriter @ 2023-05-17 22:19:33