/in/foo.cc: In function 'void Find()':
/in/foo.cc:25:40: warning: operation on 'xb_2' may be undefined [-Wsequence-point]
   25 |                 if (IsPrime[i]) primes[++xb_2]=primes[xb_2-1]+i,prime.push_back(i);
      |                                        ^~~~~~
/in/foo.cc:25:40: warning: operation on 'xb_2' may be undefined [-Wsequence-point]
/in/foo.cc:26:29: warning: operation on 'xb_2' may be undefined [-Wsequence-point]
   26 |                 else primes[++xb_2]=primes[xb_2-1];
      |                             ^~~~~~
/in/foo.cc:26:29: warning: operation on 'xb_2' may be undefined [-Wsequence-point]
/in/foo.cc:27:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |                 for (int j=0;j<prime.size()&&i*prime[j]<maxx;j++)
      |                              ~^~~~~~~~~~~~~
/in/foo.cc: In function 'bool pdrun(int)':
/in/foo.cc:38:31: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   38 |         return a%400==0||a%100&&a%4==0;
      |                          ~~~~~^~~~~~~~