#include<stdio.h>

void print_stars();

void option_list();

void divisors(int n);

int summation(int s);

int factorial (int n) ;

int main(void) {

                int           number , result , op  ;

                char flag;

                printf("Enter an integer number > ");

                scanf( "%d" , &number );

                do{

                                option_list();

                                scanf("%d" , &op);

                                switch(op)             {

                                                case 1:

                                                                divisors(number);

                                                                break;

                                                case 2:

                                                                result = summation(number) ;

                                                                printf("Summation = %d\n" , result);

                                                                break;

                                                case 3:

                                                                result = factorial(number) ;

                                                                printf("Factorial = %d\n" , result);

                                                                break;

                                                default:

                                                                printf("\nERROR: %d is unrecognized option!!! \n" , op);

                                }

                                print_stars();

                                printf("Do you want to check another function? (Y/N)> ");

                                scanf(" %c" , &flag);

                } while (flag == 'Y' || flag == 'y');

                return 0;

}

void option_list(){

                print_stars();

                printf("1: Find the divisors \n");

                printf("2: Compute the summuation\n");

                printf("3: Compute the factorial \n");

                print_stars();

                printf("Please enter your choice: ");

}

void print_stars(){

                int i;

                for(i = 1 ; i <= 25 ; i++)

                                printf("*");

                printf("\n");

}

void divisors(int n)  {

                int i;

                printf("Divisors of %d are\n",n);

                for(i=1;i<=n;i++)

                                if(n%i==0)

                                                printf(" %d",i);

                printf("\n");

}

int factorial (int n){

int i , fact = 1 ;

                for (i = 2 ; i <= n ; i++)

                                fact *= i;

                return fact;

}

int summation(int s){

if (s == 0)

             return 0;

                else

                                return  s + summation(s-1);

}