#include <stdio.h>

main(){
	int N,d=1,i;
	do{
		printf ("Nhap so nguyen duong N: ");
    	scanf ("%d",&N);
	}
 	while(N<=0);

 	while (N!=0){
 		i=N%10;
 		N=N/10;
 		if((N!=0)&&(i>N%10)){
 			d=0;
 			break;
 		}
 	}
 	if(d==1)
	 	printf ("\nSo vua nhap la so lui");
 	else
	 	printf ("\nSo vua nhap khong la so lui");
}