/in/foo.cc: In function 'int Max()':
/in/foo.cc:15:9: warning: 'index' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return index;
         ^~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:33:14: warning: 'index' may be used uninitialized in this function [-Wmaybe-uninitialized]
    if(a[index+1]>=a[index-1] && a[index-1]<avg){
         ~~~~~^~