foo.cc: In function 'int main()':
foo.cc:141:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
     int mid=l+r+1>>1;
             ~~~^~
foo.cc:123:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%s",s+1),n=strlen(s+1);
  ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
foo.cc:132:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf(" %c ",&opt),read(x);
   ~~~~~~~~~~~~~~~~~~^~~~~~~~
foo.cc:151:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf(" %c ",&c);
    ~~~~~^~~~~~~~~~~
foo.cc:156:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf(" %c ",&c);
    ~~~~~^~~~~~~~~~~

正在同步测试数据，请稍后
[Hydro](https://hydro.ac)提供评测服务