foo.cc: In function 'int main()':
foo.cc:15:30: warning: left operand of comma operator has no effect [-Wunused-value]
   15 |                 for(int j=0;j<n,j++)
      |                             ~^~
foo.cc:15:36: error: expected ';' before ')' token
   15 |                 for(int j=0;j<n,j++)
      |                                    ^
      |                                    ;
foo.cc:17:32: error: lvalue required as left operand of assignment
   17 |                         if(a[i]-a[j]=x)
      |                            ~~~~^~~~~

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