fn main(){
   let mut a = [1,2,3,4,5];
   a_mul(&mut a);
   println!("{:?}",a);
   
   
   fn a_mul(p: &mut [i32;5]){
       let mut i = 0;
       while i<p.len()
       {
           p[i] *= 3;
           i += 1;
       }
   }
}