/in/foo.cc: In function 'void dfs(int, std::__cxx11::string)':
/in/foo.cc:72:11: warning: unused variable 'a' [-Wunused-variable]
       int a = s[i]-'0', b = s[j]-'0';
           ^
/in/foo.cc:72:25: warning: unused variable 'b' [-Wunused-variable]
       int a = s[i]-'0', b = s[j]-'0';
                         ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:153:14: warning: unused variable 'cnt' [-Wunused-variable]
   int ans=0, cnt=0;
              ^~~