#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
using namespace std;
template <typename T>
T sqr(T a) {
  return a * a;
}
template <typename T>
int sign(T a) {
  if (a == 0) return 0;
  return (a > 0 ? 1 : -1);
}
template <typename T>
bool uax(T& a, const T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
bool uin(T& a, const T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T1, typename T2>
istream& operator>>(istream& in, pair<T1, T2>& p) {
  in >> p.first >> p.second;
  return in;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& out, pair<T1, T2>& p) {
  out << p.first << ' ' << p.second;
  return out;
}
mt19937_64 rnd(0);
const int LOG = 64;
const int N = (int)2e5 + 7;
const int MAXN = (int)2e5;
const int MOD = (int)1e9 + 7;
const int INF = (int)2e9 + 7;
const int CONST = 450;
const long long LINF = (int64_t)1e18;
const long double PI = 3.1415926535897932384626433832795;
const long double EPS = 1;
int n;
long long a[N], b[N], suma, sumb;
bool check_straight() {
  bool fl = true;
  for (int i = 0; i < n; i++) fl &= a[i] == b[i];
  return fl;
}
bool check_reverse() {
  bool fl = true;
  for (int i = 0; i < n; i++) fl &= a[i] == b[n - i - 1];
  return fl;
}
void unpref() {
  long long val = b[0];
  for (int i = 1; i < n; i++) {
    b[i] -= val;
    val += b[i];
  }
  sumb = val;
}
void solve2() {
  long long pref = 0;
  vector<long long> len;
  while (true) {
    if (check_straight()) break;
    if (check_reverse()) {
      len.push_back(0);
      break;
    }
    bool str = true, rev = true;
    for (int i = 1; i < n; i++) {
      str &= b[i] > b[i - 1];
      rev &= b[i] < b[i - 1];
    }
    if (!str && !rev) {
      cout << "IMPOSSIBLE";
      return;
    }
    if (str) {
      long long un = (b[1] - 1) / b[0];
      if (b[0] + b[1] - un * b[0] > a[0] + a[1]) {
        len.push_back(un);
        pref += un;
        b[1] -= un * b[0];
        continue;
      }
      long long val = b[0] + b[1] - a[0] - a[1];
      if (val % b[0]) {
        cout << "IMPOSSIBLE";
        return;
      }
      un = val / b[0];
      pref += un;
      len.push_back(un);
      b[1] -= b[0] * un;
      if (check_straight()) break;
      if (check_reverse()) {
        len.push_back(0);
        break;
      }
      cout << "IMPOSSIBLE";
      return;
    } else {
      len.push_back(0);
      reverse(b, b + n);
    }
  }
  reverse(len.begin(), len.end());
  if (pref > MAXN)
    cout << "BIG\n" << pref;
  else {
    cout << "SMALL\n";
    long long sumlen = 0;
    for (long long x : len) sumlen += max(x, 1LL);
    cout << sumlen << "\n";
    for (long long x : len) {
      if (x == 0) {
        cout << 'R';
        continue;
      }
      while (x--) cout << 'P';
    }
  }
}
void solve() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    suma += a[i];
  }
  for (int i = 0; i < n; i++) {
    cin >> b[i];
    sumb += b[i];
  }
  if (n == 1) {
    if (a[0] == b[0])
      cout << "SMALL\n0";
    else
      cout << "IMPOSSIBLE";
    return;
  }
  if (n == 2) {
    solve2();
    return;
  }
  int pref = 0;
  string ans = "";
  while (true) {
    if (suma > sumb) {
      cout << "IMPOSSIBLE";
      return;
    }
    if (check_straight()) break;
    if (check_reverse()) {
      ans += 'R';
      break;
    }
    bool str = true, rev = true;
    for (int i = 1; i < n; i++) {
      str &= b[i] > b[i - 1];
      rev &= b[i] < b[i - 1];
    }
    if (!str && !rev) {
      cout << "IMPOSSIBLE";
      return;
    }
    if (str) {
      pref++;
      ans += 'P';
      unpref();
    } else {
      ans += 'R';
      reverse(b, b + n);
    }
  }
  reverse(ans.begin(), ans.end());
  if (pref > MAXN)
    cout << "BIG\n" << pref;
  else
    cout << "SMALL\n" << (int)ans.size() << "\n" << ans;
}
int main() {
  double start = clock();
  cout << fixed << setprecision(20);
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  rnd.seed(time(0));
  int t = 1;
  for (int i = 0; i < t; i++) {
    solve();
  }
}
