/in/foo.cc: In function 'int main()':
/in/foo.cc:6:12: warning: right operand of comma operator has no effect [-Wunused-value]
  cin>>x1,x2;
            ^
/in/foo.cc:7:2: error: 'y1' was not declared in this scope
  y1=x1+x2;
  ^~
/in/foo.cc:8:2: error: 'y2' was not declared in this scope
  y2=x1*x2;
  ^~
/in/foo.cc:9:2: error: 'y3' was not declared in this scope
  y3=x1%x2;
  ^~