main(){
 int num1;
 int num2;
 real s;
 real r;
 real p;
 char n;
 n='M';
 num1=2;
 num2=4;
 if num1!=2 
   if num2<=3
    num1=num1+2;
     else
    num1=num1-(num2+1); //<算術(shù)表達(dá)式>－<項>
     p=3.1415;
      r=10.0;
      s=p*r*r;  /*求圓的面積*/
}