answer.code:4:1: error: ‘vector’ does not name a type
    4 | vector<int> A;
      | ^~~~~~
answer.code: In function ‘int count_ways(int, int)’:
answer.code:11:17: error: ‘A’ was not declared in this scope
   11 |                 A[i-N] = A[i-N]^1;
      |                 ^
answer.code:11:21: error: ‘N’ was not declared in this scope
   11 |                 A[i-N] = A[i-N]^1;
      |                     ^
answer.code:14:19: error: ‘N’ was not declared in this scope
   14 |         for(int i=N;i<N+M;i++){
      |                   ^
answer.code:14:25: error: ‘M’ was not declared in this scope
   14 |         for(int i=N;i<N+M;i++){
      |                         ^
answer.code:15:20: error: ‘A’ was not declared in this scope
   15 |                 if(A[i]==1){
      |                    ^