foo.cc: In function 'int main()':
foo.cc:48:28: warning: integer overflow in expression [-Woverflow]
             int ans=(1<<31)-1;
                     ~~~~~~~^~
foo.cc:41:22: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
                 b = b*10+arr[i];
                     ~^~~
foo.cc:37:22: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]
                 a = a*10 + arr[i];
                     ~^~~

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