View Compilation Error

0_0_33641185_16338.cpp: In function 'void conduct(char*, char*)':
0_0_33641185_16338.cpp:26:23: error: 'strlen' was not declared in this scope
  int L = 2 * strlen(os) + 1;
                       ^
0_0_33641185_16338.cpp: In function 'int main()':
0_0_33641185_16338.cpp:43:20: error: 'strlen' was not declared in this scope
   int L = strlen(os);
                    ^