/in/foo.cc: In function 'int main()':
/in/foo.cc:49:3: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(str);
   ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:49:11: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(str);
           ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:52:23: error: 'isalnum' was not declared in this scope
   while(isalnum(str[j]))
                       ^
/in/foo.cc:62:24: error: 'isalnum' was not declared in this scope
    while(isalnum(str[j])) y=y*10+str[j]-'0',++j;
                        ^