11417 - GCD

Problem A
GCD
Input: Standard Input

Output: Standard Output

 

Given the value of N, you will have to find the value of G. The definition of G is given below:

 

Here GCD(i,j) means the greatest common divisor of integer i and integer j.

 

For those who have trouble understanding summation notation, the meaning of G is given in the following code:

G=0; for(i=1;i<N;i++) for(j=i+1;j<=N;j++) {     G+=GCD(i,j); } /*Here GCD() is a function that finds the greatest common divisor of the two input numbers*/

 

Input

The input file contains at most 100 lines of inputs. Each line contains an integer N (1<N<501). The meaning of N is given in the problem statement. Input is terminated by a line containing a single zero.  This zero should not be processed.

 

Output

For each line of input produce one line of output. This line contains the value of G for corresponding N.

 

Sample Input                              Output for Sample Input

10 100 500 0

67 13015 442011

#include<stdio.h>

int gcd(int a, int b)

{

	if(!b) return a;

	return gcd(b,a%b);

}

int main()

{

	int n;

	while (scanf("%d",&n)&&n)

	{

		int g=0,i,j;

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

			for(j=i+1;j<=n;j++)

				g+=gcd(j,i);

		printf("%d\n",g);

	}

	return 0;

}