foo.cc: In function 'int get_sta(int)':
foo.cc:54:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for (int i=1;p[i]<=x;i++) {
              ~~~~^~~
foo.cc: In function 'int main()':
foo.cc:84:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(k=1;k<max(2,tmp*2-1);k++) //注意当tmp==1时tmp*2-2=0!
         ~^~~~~~~~~~~~~~~
foo.cc:73:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n);
 ~~~~~^~~~~~~~~
foo.cc:80:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&tmp);
 ~~~~~^~~~~~~~~~~

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