Display the pattern like Right angle Triangle with a Number

#include <stdio.h>
void main()
{
   int a,b,rows;
   printf("Input number of Rows : ");
   scanf("%d",&rows);
   for(a=1;a<=rows;a++)
   {
	for(b=1;b<=a;b++)
	   printf("%d",b);
	printf("\n");
   }
}