foo.cc: In function 'int main()':
foo.cc:11:6: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  if(x=y)
     ~^~
foo.cc:5:14: warning: variable 'b' set but not used [-Wunused-but-set-variable]
  int a,x,y,z,b;
              ^

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