/in/foo.cc: In function 'int suan()':
/in/foo.cc:19:22: warning: 'pos' may be used uninitialized [-Wmaybe-uninitialized]
   19 |         x[++px]=a[pos]; y[++py]=a[pos+1];
      |                 ~~~~~^
/in/foo.cc:13:21: note: 'pos' was declared here
   13 |         int sub=20, pos;
      |                     ^~~