View Compilation Error

0_0_33527418_7741.cpp: In function 'void work()':
0_0_33527418_7741.cpp:8:18: error: 'strlen' was not declared in this scope
  int n=strlen(s+1);
                  ^
0_0_33527418_7741.cpp:32:29: error: 'mul' was not declared in this scope
   Ans=add(Ans,mul(tmp,ans[i]));
                             ^
0_0_33527418_7741.cpp:32:30: error: 'add' was not declared in this scope
   Ans=add(Ans,mul(tmp,ans[i]));
                              ^
0_0_33527418_7741.cpp: In function 'int main()':
0_0_33527418_7741.cpp:39:13: error: 'read' was not declared in this scope
  int T=read(); while(T--) work();
             ^