#include <bits/stdc++.h>
using namespace std;
const int N = 33;
int n, r, fib[N], ans = 1 << 25, best, type;
vector<char> v;
long long gcd(long long firstnum, long long secondnum) {
  return (secondnum == 0) ? firstnum : gcd(secondnum, firstnum % secondnum);
}
int gcd2(int a, int b) {
  if (a == 1) return max(0, b - 2);
  if (b == 1) return max(0, a - 1);
  int cnt = 0;
  if (a > b) {
    cnt = a / b - 1;
    return cnt + gcd2(a % b, b);
  } else {
    cnt = b / a - 1;
    return cnt + gcd2(a, b % a);
  }
}
int gcd3(int a, int b) {
  if (a == 1) {
    for (int i = 0; i < max(0, b - 1); i++) v.push_back('B');
    return max(0, b - 2);
  }
  if (b == 1) {
    for (int i = 0; i < max(0, a); i++) v.push_back('T');
    return max(0, a - 1);
  }
  int cnt = 0;
  if (a > b) {
    cnt = a / b - 1;
    for (int i = 0; i <= cnt; i++) {
      v.push_back('T');
    }
    return cnt + gcd3(a % b, b);
  } else {
    cnt = b / a - 1;
    for (int i = 0; i <= cnt; i++) {
      v.push_back('B');
    }
    return cnt + gcd3(a, b % a);
  }
}
int gcd4(int a, int b) {
  if (a == 0) return 0;
  if (b == 0) return 0;
  if (a > b) {
    return a / b + gcd4(a % b, b);
  }
  return b / a + gcd4(a, b % a);
}
int main() {
  if (fopen("B.in", "r")) freopen("B.in", "r", stdin);
  cin >> n >> r;
  if (n == 1 && r == 1) {
    cout << 0 << endl;
    cout << 'T';
    return 0;
  }
  fib[0] = 0;
  fib[1] = 1;
  for (int i = 2; i < N; i++) {
    fib[i] = fib[i - 1] + fib[i - 2];
  }
  for (int i = 1; i < r; i++) {
    if (gcd(i, r) != 1) continue;
    if (gcd4(i, r) == n) {
      int cur = gcd2(i, r);
      if (cur < ans) {
        ans = cur;
        best = i;
        type = 0;
      }
    }
    if (gcd4(r, i) == n) {
      int cur = gcd2(r, i);
      if (cur < ans) {
        ans = cur;
        best = i;
        type = 1;
      }
    }
  }
  if (ans == 1 << 25) {
    cout << "IMPOSSIBLE";
    return 0;
  }
  cout << ans << endl;
  cout << 'T';
  if (type == 0) {
    gcd3(best, r);
  } else {
    gcd3(r, best);
  }
  for (int i = v.size() - 1; i >= 0; i--) cout << v[i];
  return 0;
}
