1 #include<cstdio>
2 #include<iostream>
3 #include<cstring>
4 #include<algorithm>
5
6 using namespace std;
7
8 int len, m, n, a[500005];
9
10 inline int check(int x){
11 int cnt = 0, last = 0;
12 for(int i = 1; i <= n + 1; i++){
13 if(a[i] - a[last] < x) cnt++;
14 else last = i;
15 }
16 if(cnt <= m) return 1;
17 return 0;
18 }
19
20 int main(){
21 while(scanf("%d%d%d", &len, &n, &m) != EOF){
22 memset(a, 0, sizeof(a));
23 a[n + 1] = len;
24 for(int i = 1; i <= n; i++){
25 scanf("%d", &a[i]);
26 }
27 sort(a + 1, a + n + 1);
28 int l = 1, r = len, ans;
29 while(l <= r){
30 int mid = (l + r) >> 1;
31 if(check(mid)) {ans = mid; l = mid + 1;}
32 else r = mid - 1;
33 }
34 printf("%d
", ans);
35 }
36 return 0;
37 }
