View Compilation Error

0_0_38929774_22651.cpp: In function 'void dfs(std::string, std::string, long long int, long long int)':
0_0_38929774_22651.cpp:36:15: error: 'std::string' {aka 'class std::__cxx11::basic_string<char>'} has no member named 'b'
   36 |         dfs(a.b.f+1,pos+1);
      |               ^
0_0_38929774_22651.cpp: In function 'int main()':
0_0_38929774_22651.cpp:61:16: error: expected ';' before '}' token
   61 |         slove()
      |                ^
      |                ;
   62 |     }
      |     ~