#include <cstdio>
#include <iostream>
#include <queue>
#include <cmath>
using namespace std;
int n;
long long fai(int x){
long long re=x;
for(int i=2;i<=sqrt(x);++i){
if(x%i==0){
re=re*(i-1)/i;
}
while(x%i==0) x/=i;
}
if(x!=1) re=re*(x-1)/x;
return re;
}
int main(){
scanf("%d",&n);
printf("%lld",fai(n));
return 0;
}