foo.cc: In function 'void solve()':
foo.cc:17:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define F(i,start,end) for(R int (i)=(start);(i)<=(end);i++)
                                              ~~~^~~~~~~
foo.cc:59:2: note: in expansion of macro 'F'
  F(i,0,s.size()-1)
  ^
foo.cc:95:6: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(z&&!f1||f1&&z!=x)
     ~^~~~~

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