foo.cc: In function 'int find(int)':
foo.cc:12:26: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   12 |                 int mid=l+r>>1;
      |                         ~^~
foo.cc:16:16: warning: 'pos' may be used uninitialized [-Wmaybe-uninitialized]
   16 |         return pos;
      |                ^~~
foo.cc:10:25: note: 'pos' was declared here
   10 |         int l=1,r=2*m+n,pos;
      |                         ^~~

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