depou

#include <iostream>
using namespace std;
int A[1001], B[1001], C[1001];

struct drum {
    char x, y;
}v[1001];


int main()
{
    int n, op = 0, c = 0, b = 0;
    cin >> n;
    for (int i = 0; i < n; i++)
        cin >> A[i];

    for (int i = n - 1; i >= 0; i--)
    {
        if (A[i] == 1)
        {
            C[c++] = A[i];
            v[op].x = 'A';
            v[op].y = 'C';
            op++;
        }
        else
        {
            if (A[i] == C[c - 1] + 1 && c)
            {
                C[c++] = A[i];
                v[op].x = 'A';
                v[op].y = 'C';
                op++;
            }
            else
            {
                {
                    B[b++] = A[i];
                    v[op].x = 'A';
                    v[op].y = 'B';
                    op++;
                }
            }
        }

    }


    for (int i = b - 1; i >= 0; i--)
    {
        C[c++] = B[i];
        v[op].x = 'B';
        v[op].y = 'C';
        op++;
    }

        for (int i = 1; i < c; i++)
        if (C[i] != C[i - 1] + 1)
            op = 0;


    cout << op << "\n";
    if(op)
    for (int i = 0; i < op; i++)
        cout << v[i].x << " " << v[i].y << "\n";


    return 0;
}