
public class functions {
		static int tong(int a,int b){
			return a+b;
		}
		static int dem(int n){
			int d=0;
			do {
				n=n/10;
				d=d+1;
			}while (n!=0);
			return d;
			
		}
		static void hienthi(int n){
			System.out.println(n);
		}
		static void daonguocso (int n){
			int d;
			do{
			//d=n;
			d=n%10;
			System.out.print(d);
			n=n/10;
			}while(n!=0);
		}
		static void sohoanthien (int n){
			int tong;
			tong=0;
			
			for (int i=1;i<n;i++){
				if(n%i==0){
					tong=tong+i;
				}
			}
			if(tong==n){
				System.out.println(n+" chinh la so hoan thien");
			}else {System.out.println(n+" ko phai so hoan thien");}
				
		}
		static boolean sochinhphuong (float a){
			int t2;
			boolean kt=false;
			t2=(int)Math.sqrt(a);
			if (t2==Math.sqrt(a)){
				kt = true;
			}
			return kt;
		} 
		static boolean kiemtrasonguyento (int n){
			boolean kq=true;
			for (int i=2;i<n;i++){
				if (n%i==0){
					kq=false;
					
				}
			}
			return kq;
			}
		static void phantich (int n) {
			int i = 2;
			while (n>1){
				if (kiemtrasonguyento(i)==true){
					if (n%i==0){
						System.out.print(i+".");
						n=n/i;
					}else i++;
				}else i++;
			}
		}
}

