Codeforces 339E

 #include <cstdio>
 #include <algorithm>
 #include <cmath>
 #include <cstring>
 #include <cstdlib>
 #include <ctime>
 #include <set>
 #include <map>
 using namespace std;

 const int maxn=;

 struct point
 {
     int x, y;
 };

 int n;
 int sum;
 int a[maxn], des[maxn];
 point ans[];

 void init()
 {
     scanf("%d", &n);
     a[]=; a[n+]=n+;
     for (int i=; i<=n; ++i) scanf("%d", &a[i]);
 }
 void rev(int le, int ri)
 {
     for (int i=le; i<=(ri+le)/; ++i)
         swap(a[i], a[ri-(i-le)]);
 }
 bool check()
 {
     for (int i=; i<=n; ++i)
         if (a[i]!=i) return false;
     return true;
 }
 void print(int step)
 {
     printf("%d\n", step);
     for (int i=step; i>; --i)
         printf("%d %d\n", ans[i].x, ans[i].y);
     exit();
 }
 void dfs(int k)
 {
     if (check()) print(k-);
     if (k>) return;
     for (int i=; i<n; ++i)
         for (int j=i+; j<=n; ++j)
             if (abs(a[i-]-a[j])== || abs(a[i]-a[j+])==)
             {
                 ans[k].x=i;
                 ans[k].y=j;
                 rev(i, j);
                 dfs(k+);
                 rev(i, j);
             }
 }
 int main()
 {
     freopen("input.txt", "r", stdin);
     freopen("output.txt", "w", stdout);
     init();
     dfs();
     return ;
 }