1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<algorithm>
 5 #include<cmath>
 6 using namespace std;
 7 int main()
 8 {
 9     int L,a[50050],ans;
10     int n,m,i,j,l,r,mid,k;
11     scanf("%d %d %d",&L,&n,&m);
12     for (i=1; i<=n; i++) scanf("%d",&a[i]);
13     l=0;r=L+1;
14     a[0]=0;a[n+1]=L;
15     while (l+1<r)
16     {
17         ans=0;
18         mid=(l+r)/2;
19         i=0;
20         while (i<=n)
21         {
22             j=i+1;
23             while (j<=n+1 && a[j]-a[i]<mid) j++;
24             ans+=j-i-1;
25             i=j;
26         }
27         if (ans<=m) l=mid;
28         else r=mid;
29     }
30     printf("%d",l);
31     return 0;
32 }