>     while(scanf("%d",&n),n != 0){
>         if(n == 1){
>             printf("0\n");  continue;
>         }
>         ans = n;
>         for(int i = 2;i*i <= n;++i){
>             if( n % i == 0 ){
>                 ans = ans - ans/i;
>                 while(n%i == 0){
>                     n /= i;
>                 }
>             }
>         }
>         // n is prime itself
>         if(n != 1)  ans = ans - ans / n;
>         printf("%d\n",ans);
>     }