uva 12493

本來以為是一筆畫圖形，結果完全不是...

因為要走完所有的點 而且每一步都是一樣長的，所以走的步數要跟總共的點互質

否則最大公因數如果不是1代表不到n步就走完了

 

其實是歐拉公式

取出n的所有質因數a1,a2,a3

並且用公式n2=n(1-1/a1)*(1-1/a2)*(1-1/a3)

這就等於把質因數全部的倍數刪掉 取出剩下的數

//============================================================================
// Name        : stars2.cpp
// Date : 2013/3/22 上午11:47:39
// Author : GCA
//============================================================================
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
#ifdef ONLINE_JUDGE
#define ll "%lld"
#else
#define ll "%I64d"
#endif
typedef unsigned int uint;
typedef long long int Int;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
    printf("%d ",dp[htx][hty]);}Pln();}
#define M 10000000
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define Is_debug true
#define debug(...) if(Is_debug)printf("DEBUG: "),printf(__VA_ARGS__)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
    int tmp=min(x,y);
    return min(tmp,z);
}
int max3(int x,int y,int z){
    int tmp=max(x,y);
    return max(tmp,z);
}
int n;
vector<int> a;
void solve(){
    int on=n;
    int sqrtn=sqrt(n);
    for(int i=2;i<=sqrtn;i++){
        if(!(n%i)){
            while(!(n%i)) n/=i;
            a.PB(i);
        }
    }
    if(n!=1)a.PB(n);
    int size=a.size();
    for(int i=0;i<size;i++){
//        debug("%d\n",a[i]);
        on=on-on/a[i];
    }
    printf("%d\n",on>>1);
}
int main() {
    ios_base::sync_with_stdio(0);
    while(~scanf("%d",&n)){
        solve();
        a.clear();
    }

















}