View Compilation Error

0_0_30293783_13750.cpp: In function 'int main()':
0_0_30293783_13750.cpp:13:22: error: 'ch' was not declared in this scope
         scanf("%s%s",ch,dex);
                      ^
0_0_30293783_13750.cpp:14:23: error: 'strlth' was not declared in this scope
         lth1=strlth(ch);
                       ^