try yourself |run program

#include <stdio.h>
#include <conio.h>

void main(){
 int a,b;
 int *p1, **p2, *pp1, **pp2;
 int s1,s2,s3;
 clrscr();
  printf("\nenter value of a: ");
 scanf("%d",&a);
 printf("\nenter value of b: ");
 scanf("%d",&b);
  p1 = &a ;
 p2 = &p1 ;
  pp1 = &b ;
  pp2 = &pp1 ;
  s1 = **p2 + **pp2;
 s2 = *p1 + **pp2;
 s3 = s1 + s2;
 printf("\n value of s1 = %d",s1);
 printf("\n value of s2 = %d",s2);
 printf("\n value of s3 = %d",s3);
 getch();
}

Program Output

enter value of a: 10
enter value of b: 20
value of s1 = 30
value of s2 = 30
value of s3 = 60