foo.cc: In function 'int main()':
foo.cc:25:5: error: redefinition of 'int main()'
 int main()
     ^~~~
foo.cc:17:5: note: 'int main()' previously defined here
 int main()
     ^~~~
foo.cc:31:15: error: 'walk' was not declared in this scope
         cout<<walk(n)<<endl;
               ^~~~
foo.cc:28:9: warning: unused variable 'm' [-Wunused-variable]
     int m=1;
         ^

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