#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


/*
  xyz
  0123
  
  012
  xyz3
  
  yz3
  x012
*/

char buf[300'010];

int N, K;
string S[2];

int mod(int x) {
  return ((x %= N) < 0) ? (x + N) : x;
}

int main() {
  for (; ~scanf("%d%d", &N, &K); ) {
    for (int h = 0; h < 2; ++h) {
      scanf("%s", buf);
      S[h] = buf;
    }
#ifdef LOCAL
string judge[2]={S[0],S[1]};
#endif
    
    // S[0] ~~> B^N
    int cntC = count(S[0].begin(), S[0].end(), 'C');
    const bool sw = (2 * cntC > N);
    if (sw) {
      swap(S[0], S[1]);
      cntC = N - cntC;
    }
    
    vector<pair<int, int>> ops;
    auto oper = [&](int x, int y) -> void {
      x = mod(x);
      y = mod(y);
      if (sw) {
        swap(x, y);
      }
      ops.emplace_back(x, y);
#ifdef LOCAL
for(int k=0;k<K;++k)swap(judge[0][mod(x+k)],judge[1][mod(y+k)]);
cerr<<COLOR("33")<<x<<" "<<y<<" "<<judge[0]<<" "<<judge[1]<<COLOR()<<endl;
#endif
    };
    
    // S[0][x, x+K), S[1][y, y+K+1)
    int x = 0, y = 0;
    deque<char> bs(S[0].begin(), S[0].begin() + K);
    deque<char> cs(S[1].begin(), S[1].begin() + (K + 1));
    for (; cntC--; ) {
      for (; bs.front() == 'B'; ) {
        --x;
        S[0][mod(x + K)] = bs.back();
        bs.pop_back();
        bs.push_front(S[0][mod(x)]);
      }
      for (; cs.back() == 'C'; ) {
        S[1][mod(y)] = cs.front();
        cs.pop_front();
        cs.push_back(S[1][mod(y + K + 1)]);
        ++y;
      }
      oper(x, y);
      oper(x, y + 1);
      bs.pop_front();
      bs.push_back('B');
      cs.pop_back();
      cs.push_front('C');
    }
    
    printf("%d\n", (int)ops.size());
    for (const auto &op : ops) {
      printf("%d %d\n", op.first + 1, op.second + 1);
    }
  }
  return 0;
}