/*while(x<>2)
    x := x + 1;
    
while(x>2){
    print(x);
    print(x);
    read(x)
    };
    */

x := 49 ; y := 21 ; while (x <> y)
case when (x < y)  y := y - x
when (x > 2) print(y)
else x := x - y