# Problem E: Relatives

Problem E: Relatives

## Problem E: Relatives

Given n, a positive integer, how many positive integers less than n are relatively prime to n? Two integers a and b are relatively prime if there are no integers x > 1, y > 0, z > 0 such that a = xy and b = xz.

There are several test cases. For each test case, standard input contains a line with n <= 1,000,000,000. A line containing 0 follows the last case.

For each test case there should be single line of output answering the question posed above.

``````7
12
0
``````

``````6
4
``````

``````#include <stdio.h>

main(){
int n,i,sum;
while (1 == scanf("%d",&n) && n) {
sum = n;
for (i=2;i*i <= n;i++) {
if (n%i == 0) {
sum -= sum/i;
}
while (n%i == 0) n /= i;
}
if (n > 1) sum -= sum/n;
printf("%d\n",sum);
}
}
``````

``````#include <stdio.h>

main(){
int n,i,sum;
while (1 == scanf("%d",&n) && n) {
sum = n;
for (i=2;i*i <= n;i++) {
if (n%i == 0) {
sum -= sum/i;
}
while (n%i == 0) n /= i;
}
if (n > 1) sum -= sum/n;
printf("%d\n",sum);
}
}
``````