foo.cc: In member function 'void ac::build()':
foo.cc:25:27: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     for(i=0;i<26;i++) if(y=ch[x][i]){
                          ~^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:40:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc: In member function 'void ac::ins(int)':
foo.cc:11:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%s",s+1);int now=0,len=strlen(s+1);
   ~~~~~^~~~~~~~~~

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