func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MN = 51;   char a[MN][MN], b[MN][MN];   const char L =  L , R =  R , U =  U , D =  D ;   vector<pair<int, int> > sol, sol2;   int n, m;   void show() {     ;     for (int i = 0; i < n; ++i)       ;     ;     ;     for (int i = 0; i < n; ++i)       ;     ;   }   bool move(char arr[MN][MN], int i, int j) {     ;     if (arr[i][j] == U && arr[i][j + 1] == U && arr[i + 1][j] == D &&         arr[i + 1][j + 1] == D) {       ;       arr[i][j] = arr[i + 1][j] = L;       arr[i][j + 1] = arr[i + 1][j + 1] = R;     } else if (arr[i][j] == L && arr[i + 1][j] == L && arr[i][j + 1] == R &&                arr[i + 1][j + 1] == R) {       ;       arr[i][j] = arr[i][j + 1] = U;       arr[i + 1][j] = arr[i + 1][j + 1] = D;     } else {       ;       return false;     }     sol.emplace_back(i, j);     return true;     ;     show();   }   void push(char arr[MN][MN], int i, int k, bool ver) {     char aim = ver ? U : L;     ;     show();     assert(arr[i][k] == L || arr[i][k] == U);     if (arr[i][k] != aim) {       if (!move(arr, i, k)) {         push(arr, i + ver, k + !ver, !ver);         move(arr, i, k);       }     }   }   int main() {     scanf( %d%d , &n, &m);     for (int i = 0; i < n; ++i) scanf( %s , a[i]);     for (int i = 0; i < n; ++i) scanf( %s , b[i]);     if (n % 2) {       ;       for (int k = 0; k < m; k += 2)         for (int i = 0; i < n; ++i) push(a, i, k, false);       swap(sol, sol2);       ;       for (int k = 0; k < m; k += 2)         for (int i = 0; i < n; i++) push(b, i, k, false);     } else {       ;       for (int i = 0; i < n; i += 2)         for (int k = 0; k < m; k++) push(a, i, k, true);       swap(sol, sol2);       ;       for (int i = 0; i < n; i += 2)         for (int k = 0; k < m; k++) push(b, i, k, true);     }     printf( %d n , (int)(sol.size() + sol2.size()));     reverse(sol.begin(), sol.end());     for (auto x : sol2) printf( %d %d n , x.first + 1, x.second + 1);     for (auto x : sol) printf( %d %d n , x.first + 1, x.second + 1);   }   