foo.cc: In function 'int main()':
foo.cc:12:14: warning: comparison of constant '15' with boolean expression is always true [-Wbool-compare]
  else if(5<=x<15)
          ~~~~^~~
foo.cc:12:11: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  else if(5<=x<15)
          ~^~~
foo.cc:16:15: warning: comparison of constant '25' with boolean expression is always true [-Wbool-compare]
  else if(15<=x<25)
          ~~~~~^~~
foo.cc:16:12: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  else if(15<=x<25)
          ~~^~~
foo.cc:18:6: warning: statement has no effect [-Wunused-value]
   x*x-200;
   ~~~^~~~
foo.cc:22:6: warning: statement has no effect [-Wunused-value]
   800-15*x;
   ~~~^~~~~

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