Problem: There are two strings s and t, consisting only of letters a and b. You can make the following operation several times: choose a prefix of s, a prefix of t and swap them. Prefixes can be empty, also a prefix can coincide with a whole string. 

Your task is to find a sequence of operations after which one of the strings consists only of a letters and the other consists only of b letters. The number of operations should be minimized.

Input

The first line contains a string s (1 ≤ |s| ≤ 2·105).

The second line contains a string t (1 ≤ |t| ≤ 2·105).

Here |s| and |t| denote the lengths of s and t, respectively. It is guaranteed that at least one of the strings contains at least one a letter and at least one of the strings contains at least one b letter.

Output

The first line should contain a single integer n (0 ≤ n ≤ 5·105) — the number of operations.

Each of the next n lines should contain two space-separated integers ai, bi — the lengths of prefixes of s and t to swap, respectively.

If there are multiple possible solutions, you can print any of them. It's guaranteed that a solution with given constraints exists.

Examples

Input

bab
bb


Output

2
1 0
1 3


Input

bbbb
aaa


Output

0

Note

In the first example, you can solve the problem in two operations:

  1. Swap the prefix of the first string with length 1 and the prefix of the second string with length 0. After this swap, you'll have strings ab and bbb. 
  2. Swap the prefix of the first string with length 1 and the prefix of the second string with length 3. After this swap, you'll have strings bbbb and a. 



In the second example, the strings are already appropriate, so no operations are needed.

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class t, class u>
void chmax(t& first, u second) {
  if (first < second) first = second;
}
template <class t, class u>
void chmin(t& first, u second) {
  if (second < first) first = second;
}
template <class t>
using vc = vector<t>;
template <class t>
using vvc = vc<vc<t>>;
using pi = pair<int, int>;
using vi = vc<int>;
template <class t, class u>
ostream& operator<<(ostream& os, const pair<t, u>& p) {
  return os << "{" << p.first << "," << p.second << "}";
}
template <class t>
ostream& operator<<(ostream& os, const vc<t>& v) {
  os << "{";
  for (auto e : v) os << e << ",";
  return os << "}";
}
using uint = unsigned;
using ull = unsigned long long;
template <class t, size_t n>
ostream& operator<<(ostream& os, const array<t, n>& first) {
  return os << vc<t>(first.begin(), first.end());
}
template <int i, class T>
void print_tuple(ostream&, const T&) {}
template <int i, class T, class H, class... Args>
void print_tuple(ostream& os, const T& t) {
  if (i) os << ",";
  os << get<i>(t);
  print_tuple<i + 1, T, Args...>(os, t);
}
template <class... Args>
ostream& operator<<(ostream& os, const tuple<Args...>& t) {
  os << "{";
  print_tuple<0, tuple<Args...>, Args...>(os, t);
  return os << "}";
}
template <class t>
void print(t x, int suc = 1) {
  cout << x;
  if (suc == 1) cout << "\n";
  if (suc == 2) cout << " ";
}
ll read() {
  ll i;
  cin >> i;
  return i;
}
vi readvi(int n, int off = 0) {
  vi v(n);
  for (int i = int(0); i < int(n); i++) v[i] = read() + off;
  return v;
}
template <class T>
void print(const vector<T>& v, int suc = 1) {
  for (int i = int(0); i < int(v.size()); i++)
    print(v[i], i == int(v.size()) - 1 ? suc : 2);
}
string readString() {
  string s;
  cin >> s;
  return s;
}
template <class T>
T sq(const T& t) {
  return t * t;
}
void yes(bool ex = true) {
  cout << "Yes"
       << "\n";
  if (ex) exit(0);
}
void no(bool ex = true) {
  cout << "No"
       << "\n";
  if (ex) exit(0);
}
void possible(bool ex = true) {
  cout << "Possible"
       << "\n";
  if (ex) exit(0);
}
void impossible(bool ex = true) {
  cout << "Impossible"
       << "\n";
  if (ex) exit(0);
}
constexpr ll ten(int n) { return n == 0 ? 1 : ten(n - 1) * 10; }
const ll infLL = LLONG_MAX / 3;
const int inf = INT_MAX / 2 - 100;
int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
int topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
int botbit(signed first) { return first == 0 ? 32 : __builtin_ctz(first); }
int botbit(ll first) { return first == 0 ? 64 : __builtin_ctzll(first); }
int popcount(signed t) { return __builtin_popcount(t); }
int popcount(ll t) { return __builtin_popcountll(t); }
bool ispow2(int i) { return i && (i & -i) == i; }
int mask(int i) { return (int(1) << i) - 1; }
bool inc(int first, int second, int c) {
  return first <= second && second <= c;
}
template <class t>
void mkuni(vc<t>& v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
ll rand_int(ll l, ll r) {
  static random_device rd;
  static mt19937_64 gen(rd());
  return uniform_int_distribution<ll>(l, r)(gen);
}
template <class t>
int lwb(const vc<t>& v, const t& first) {
  return lower_bound(v.begin(), v.end(), first) - v.begin();
}
vi lens(string s) {
  vi res;
  char pre = 'c';
  for (auto c : s) {
    if (c != pre) {
      res.emplace_back(0);
      pre = c;
    }
    res.back()++;
  }
  return res;
}
void sums(vi& x) {
  for (int i = int(1); i < int(int(x.size())); i++) x[i] += x[i - 1];
}
vi shift(vi x, int off) {
  vi res(int(x.size()) + off);
  for (int i = int(0); i < int(int(x.size())); i++) res[i + off] = x[i];
  return res;
}
pair<int, vc<pi>> sub(vi x, vi y, int off, int k) {
  void(0);
  bool rev = false;
  if (x.size() < y.size()) {
    swap(x, y);
    rev = true;
  }
  if (int(y.size()) == 1 && k) return {inf, {}};
  void(0);
  void(0);
  int dif = x.size() - y.size();
  int mid = dif / 2;
  int cut = mid + off;
  if (cut < 0 || dif < cut) return {inf, {}};
  vc<pi> res;
  void(0);
  void(0);
  if (cut || k) {
    vi z(x.begin(), x.begin() + cut);
    x.erase(x.begin(), x.begin() + cut);
    vi w(y.begin(), y.begin() + k);
    y.erase(y.begin(), y.begin() + k);
    res.emplace_back(accumulate(z.begin(), z.end(), 0),
                     accumulate(w.begin(), w.end(), 0));
    if (int(x.size()) % 2 == int(y.size()) % 2) {
      if (int(z.size())) {
        z.back() += y[0];
        y.erase(y.begin());
      }
      if (int(w.size())) {
        w.back() += x[0];
        x.erase(x.begin());
      }
    }
    y.insert(y.begin(), z.begin(), z.end());
    x.insert(x.begin(), w.begin(), w.end());
  }
  void(0);
  void(0);
  sums(x);
  sums(y);
  int len = max(int(x.size()), int(y.size()));
  x = shift(x, len - int(x.size()));
  y = shift(y, len - int(y.size()));
  for (int i = int(len - 1) - 1; i >= int(0); i--) {
    res.emplace_back(x[i], y[i]);
    if ((len - 2 - i) % 2) swap(res.back().first, res.back().second);
  }
  if (rev)
    for (auto& p : res) swap(p.first, p.second);
  void(0);
  return {res.size(), res};
}
pair<int, vc<pi>> slv(string s, string t, bool rev) {
  s += 'a';
  t += 'b';
  void(0);
  vi x = lens(s), y = lens(t);
  void(0);
  void(0);
  pair<int, vc<pi>> ans(inf, {});
  for (int off = int(-4); off < int(5); off++)
    for (int k = int(0); k < int(2); k++) chmin(ans, sub(x, y, off, k));
  void(0);
  if (rev) {
    for (auto& p : ans.second) swap(p.first, p.second);
  }
  return ans;
}
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  string s, t;
  bool dbg = true;
  dbg = false;
  if (!dbg) {
    cin >> s >> t;
  } else {
    int n = 1000;
    for (int i = int(0); i < int(n); i++) s += rand_int('a', 'b');
    for (int i = int(0); i < int(n); i++) t += rand_int('a', 'b');
  }
  pair<int, vc<pi>> ans = min(slv(s, t, false), slv(t, s, true));
  print(ans.first);
  for (auto p : ans.second) {
    print(p.first, 2);
    print(p.second);
    if (dbg) {
      cout << endl;
      string x = t.substr(0, p.second) + s.substr(p.first);
      string y = s.substr(0, p.first) + t.substr(p.second);
      cerr << x << " " << y << endl;
      s = x;
      t = y;
    }
  }
}