/in/foo.cc: In function 'int main()':
/in/foo.cc:31:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
    int mid=left+right>>1;
            ~~~~^~~~~~
/in/foo.cc:39:21: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   printf("%d\n",ans);
                     ^