foo.cc: In function 'int main()':
foo.cc:36:17: error: expected primary-expression before '%' token
   36 |     while(scanf(%s%s,a,b)==2)
      |                 ^
foo.cc:36:18: error: 's' was not declared in this scope
   36 |     while(scanf(%s%s,a,b)==2)
      |                  ^

[Hydro](https://hydro.ac)提供评测服务