1 #include <cstdio>
2 #include <algorithm>
3 #include <cmath>
4 #include <cstring>
5 #include <cstdlib>
6 #include <ctime>
7 #include <set>
8 #include <map>
9 using namespace std;
10
11 const int maxn=1100;
12
13 struct point
14 {
15 int x, y;
16 };
17
18 int n;
19 int sum;
20 int a[maxn], des[maxn];
21 point ans[10];
22
23 void init()
24 {
25 scanf("%d", &n);
26 a[0]=0; a[n+1]=n+1;
27 for (int i=1; i<=n; ++i) scanf("%d", &a[i]);
28 }
29 void rev(int le, int ri)
30 {
31 for (int i=le; i<=(ri+le)/2; ++i)
32 swap(a[i], a[ri-(i-le)]);
33 }
34 bool check()
35 {
36 for (int i=1; i<=n; ++i)
37 if (a[i]!=i) return false;
38 return true;
39 }
40 void print(int step)
41 {
42 printf("%d\n", step);
43 for (int i=step; i>0; --i)
44 printf("%d %d\n", ans[i].x, ans[i].y);
45 exit(0);
46 }
47 void dfs(int k)
48 {
49 if (check()) print(k-1);
50 if (k>3) return;
51 for (int i=1; i<n; ++i)
52 for (int j=i+1; j<=n; ++j)
53 if (abs(a[i-1]-a[j])==1 || abs(a[i]-a[j+1])==1)
54 {
55 ans[k].x=i;
56 ans[k].y=j;
57 rev(i, j);
58 dfs(k+1);
59 rev(i, j);
60 }
61 }
62 int main()
63 {
64 freopen("input.txt", "r", stdin);
65 freopen("output.txt", "w", stdout);
66 init();
67 dfs(1);
68 return 0;
69 }
