pku1284 Primitive Roots

#include<iostream>#include<vector>#include<algorithm>#include<cstdio>#include<queue>#include<stack>#include<string>#include<map>#include<set>#include<cmath>#include<cassert>#include<cstring>#include<iomanip>using namespace std;#ifdef _WIN32#define i64 __int64#define out64 "%I64d\n"#define in64 "%I64d"#else#define i64 long long#define out64 "%lld\n"#define in64 "%lld"#endif/************ for topcoder by zz1215 *******************/#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)#define FFF(i,a)        for( int i = 0 ; i < (a) ; i ++)#define FFD(i,a,b)      for( int i = (a) ; i >= (b) ; i --)#define S64(a)          scanf(in64,&a)#define SS(a)           scanf("%d",&a)#define LL(a)           ((a)<<1)#define RR(a)           (((a)<<1)+1)#define pb              push_back#define CL(Q)           while(!Q.empty())Q.pop()#define MM(name,what)   memset(name,what,sizeof(name))#define read            freopen("in.txt","r",stdin)#define write           freopen("out.txt","w",stdout)const int inf = 0x3f3f3f3f;const i64 inf64 = 0x3f3f3f3f3f3f3f3fLL;const double oo = 10e9;const double eps = 10e-9;const double pi = acos(-1.0);// i64 gcd(i64 a,i64 b){return b?gcd(b,a%b):a;}i64 gcd(i64 _a, i64 _b){    if (!_a || !_b)    {        return max(_a, _b);    }    i64 _t;    while ((_t = _a % _b))    {        _a = _b;        _b = _t;    }    return _b;}i64 ext_gcd (i64 _a, i64 _b, i64 &_x, i64 &_y){    if (!_b)    {        _x = 1;        _y = 0;        return _a;    }    i64 _d = ext_gcd (_b, _a % _b, _x, _y);    i64 _t = _x;    _x = _y;    _y = _t - _a / _b * _y;    return _d;}i64 invmod (i64 _a, i64 _p){    i64 _ans, _y;    ext_gcd (_a, _p, _ans, _y);    _ans < 0 ? _ans += _p : 0;    return _ans;}const int maxn = 10000;vector<int>p;int n;bool isp(int x){    int temp = sqrt(double(x));    for(int i=0;i<p.size();i++)    {        if(p[i] > temp)        {            return true;        }        if(!(x%p[i]))        {            return false;        }    }    return true;}void init(){    p.clear();    p.pb(2);    for(int i=3;i<maxn;i++)    {        if(isp(i))        {            p.pb(i);        }    }    return ;}int phi(int x){    int ans = 1;    int temp;    int num;    for(int i=0;p[i]*p[i]<=x;i++)    {        temp = 0;        while(x%p[i]==0)        {            x/=p[i];            if(!temp)            {                temp = p[i]-1;            }            else            {                temp *= p[i];            }        }        if(temp)        {            ans*=temp;        }    }    if(x!=1)    {        ans*=x-1;    }    return ans;}int main(){    init();    while(cin>>n)    {        cout<<phi(n-1)<<endl;    }    return 0;}