#include <bits/stdc++.h>
using namespace std;
int cao[45];
char ans[1010000];
int main() {
  int n, r, i, num, a, b, fuck, anss = 1100000, temp, k = 0, t, flag, tot;
  cao[0] = 0;
  cao[1] = 1;
  for (i = 2; i <= 35; i++) cao[i] = cao[i - 1] + cao[i - 2];
  scanf("%d%d", &n, &r);
  if (n <= 32 && r > cao[n + 1])
    printf("IMPOSSIBLE\n");
  else {
    for (i = 1; i <= r; i++) {
      a = r;
      b = i;
      tot = 0;
      fuck = 0;
      while (b) {
        if (a == b) {
          a = b;
          b = 0;
          tot++;
          break;
        }
        if (a % b == 0) {
          num = a / b - 1;
          tot = tot + num;
          fuck = fuck + num - 1;
          a = b;
        } else {
          num = a / b;
          tot = tot + num;
          fuck = fuck + num - 1;
          t = a % b;
          a = b;
          b = t;
        }
      }
      if (a != 1) continue;
      if (tot == n) {
        if (fuck < anss) {
          anss = fuck;
          temp = i;
        }
      }
    }
    if (anss >= n)
      printf("IMPOSSIBLE\n");
    else {
      printf("%d\n", anss);
      a = r;
      b = temp;
      flag = 1;
      while (b) {
        if (a == b) {
          if (flag == 1)
            ans[++k] = 'T';
          else
            ans[++k] = 'B';
          break;
        } else if (a % b == 0) {
          num = a / b - 1;
          while (num) {
            if (flag == 1)
              ans[++k] = 'T';
            else
              ans[++k] = 'B';
            num--;
          }
          a = b;
        } else {
          num = a / b;
          while (num) {
            if (flag == 1)
              ans[++k] = 'T';
            else
              ans[++k] = 'B';
            num--;
          }
          t = a % b;
          a = b;
          b = t;
        }
        flag = 1 - flag;
      }
      if (ans[k] != 'T') {
        for (i = 1; i <= k; i++) {
          if (ans[i] == 'T')
            ans[i] = 'B';
          else
            ans[i] = 'T';
        }
      }
      for (i = k; i >= 1; i--) printf("%c", ans[i]);
      printf("\n");
    }
  }
  return 0;
}
