Language: C++

#include <bits/stdc++.h> // ver2.6.1
//#include <complex.h> // FFT用
//#include <boost/math/tools/minima.hpp>
//#include <boost/multiprecision/cpp_int.hpp>
//using boost::math::tools::brent_find_minima;//fmin(f,L,R,100)で最小値をmp(x,min)で取得
//using boost::multiprecision::cpp_int;//cpp_int (任意の長さのint)
#define fmin brent_find_minima
#define int long long
#define endl "\n"
#define ALL(v) (v).begin(),(v).end()
#define Vi vector<int>
#define VVi vector<Vi>
#define VVVi vector<VVi>
#define Vm vector<mint>
#define Vs vector<string>
#define Vd vector<double>
#define Pii pair<int,int>
#define Pdd pair<double,double>
#define VPii vector<Pii>
#define Tiii tuple<int,int,int>
#define VTiii vector<Tiii>
#define PQi priority_queue<int>
#define PQir priority_queue<int,vector<int>,greater<int>>
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define itos to_string
#define stoi stoll
#define FI first
#define SE second
#define cYES cout<<"YES"<<endl
#define cNO cout<<"NO"<<endl
#define cYes cout<<"Yes"<<endl
#define cNo cout<<"No"<<endl
#define cyes cout<<"yes"<<endl
#define cno cout<<"no"<<endl
#define sortr(v) sort(v,greater<>())
#define rep(i,a,b) for(int i=a;i<b;i++)
#define repeq(i,a,b) for(int i=a;i<=b;i++)
#define repreq(i,a,b) for(int i=a;i>=b;i--)
#define dem(a,b) ((a+b-1)/(b))
#define Vin(a) rep(iI,0,a.size())cin>>a[iI]
#define INF 3000000000000000000  //  3.0*10^18(MAXの1/3くらい)
#define MAX LLONG_MAX
#define PI 3.141592653589793238462
#define MOD 1000000007  //  10^9 + 7
//int MOD = 998244353; // 変更したいときはこちら
const double EPS = 1e-10;

using namespace std;

struct mint{int x;mint(int x=0):x((x%MOD+MOD)%MOD){}
mint operator-()const{return mint(-x);}
mint& operator+=(const mint a){if((x+=a.x)>=MOD)x-=MOD;return*this;}
mint& operator-=(const mint a){if((x+=MOD-a.x)>=MOD)x-=MOD;return*this;}
mint& operator*=(const mint a){(x*=a.x)%=MOD;return*this;}
mint operator+(const mint a)const{return mint(*this)+=a;}
mint operator-(const mint a)const{return mint(*this)-=a;}
mint operator*(const mint a)const{return mint(*this)*=a;}
mint pow(int t)const{if(!t)return 1;mint a=pow(t>>1);a*=a;if(t&1)a*=*this;return a;}
mint inv()const{return pow(MOD-2);}
mint& operator/=(const mint a){return*this*=a.inv();}
mint operator/(const mint a)const{return mint(*this)/=a;}};
istream& operator>>(istream& is, const mint& a) {return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) {return os << a.x;}

/* デバッグ用 */
void Vout(auto a){if(a.size()==0) cout<<"."<<endl;
else{rep(i,0,a.size()-1)cout<<a[i]<<' ';if(a.size()>0)cout<<a.back()<<endl;}return;}
void Verr(auto a){if(a.size()==0) cerr<<"."<<endl;
else{rep(i,0,a.size()-1)cerr<<a[i]<<' ';if(a.size()>0)cerr<<a.back()<<endl;}return;}
void VVout(auto a){if(a.size()==0)cout<<"."<<endl;
else{rep(i,0,a.size())Vout(a[i]);}return;}
void VVerr(auto a){if(a.size()==0)cerr<<"."<<endl;
else{rep(i,0,a.size())Verr(a[i]);}return;}
void VPout(auto a){if(a.size()==0)cout<<"."<<endl;
else{rep(i,0,a.size())cout<<a[i].FI<<' '<<a[i].SE<<endl;}return;}
void VPerr(auto a){if(a.size()==0)cerr<<"."<<endl;
else{rep(i,0,a.size())cerr<<a[i].FI<<' '<<a[i].SE<<endl;}return;}

/* 便利関数 */
int gcd(int a,int b){return b?gcd(b,a%b):a;} // 最大公約数gcd
int lcm(int a,int b){return a/gcd(a,b)*b;} // 最小公倍数lcm
int mypow(int x, int n, int m){ // 累乗x^n(mod m) O(log(n))
if(n==0)return 1;if(n%2==0)return mypow(x*x%m,n/2,m);else return x*mypow(x,n-1,m)%m;}
int scomb(int n, int r){if(r<0||r>n)return 0;if((n-r)<r)r=n-r; // nCr
int a=1;for(int i=n;i>n-r;--i){a=a*i;}for(int i=1;i<r+1;++i){a=a/i;}return a;}
Vi vis(Vi &v){Vi S(v.size()+1);rep(i,1,S.size())S[i]+=v[i-1]+S[i-1];return S;} // 累積和
int digit(int k,int i){string s = itos(k);return s[s.size()-i]-'0';} // i桁目の数字
void press(auto &v){v.erase(unique(ALL(v)),v.end());} // 圧縮
Vi zip(Vi b){int Z=b.size(); // 座標圧縮
Pii p[Z+10];int a=b.size();Vi l(a);for(int i=0;i<a;i++)
p[i]=mp(b[i],i);sort(p,p+a);int w=0;for(int i=0;i<a;i++)
{if(i&&p[i].first!=p[i-1].first)w++;l[p[i].second]=w;}return l;}
Vi beki2V(){Vi a(64);int q = 1;rep(i,0,64){a[i]=q;q*=2;}return a;}
Vi beki2 = beki2V(); // 2^n配列
int modiv(int a,int b){return a*mypow(b,MOD-2,MOD)%MOD;} // a÷b(MOD環境)
int SMALLER(Vi &a,int x){return lower_bound(a.begin(),a.end(),x)-a.begin();}
int orSMALLER(Vi &a,int x){return upper_bound(a.begin(),a.end(),x)-a.begin();}
int BIGGER(Vi &a,int x){return a.size()-orSMALLER(a,x);}
int orBIGGER(Vi &a,int x){return a.size()-SMALLER(a,x);}
int COUNT(Vi &a,int x) {return upper_bound(ALL(a),x)-lower_bound(ALL(a),x);}
int maxind(Vi &a){return max_element(ALL(a))-a.begin();}
int minind(Vi &a){return min_element(ALL(a))-a.begin();}
Vi stpowV(){Vi a(300005);
a[0]=1;repeq(i,1,300004)a[i]=a[i-1]*i%MOD;return a;}
//Vi stpow = stpowV(); // 階乗配列(%MOD)

/****************************** START ******************************/

vector<pair<int,int>> facc(int n) { // 素因数分解
 vector<Pii>r;for(int i=2;i*i<=n;++i){if(n%i)continue;r.emplace_back(i,0);while(n%i==0){
 n/=i;r.back().second++;}}if(n!=1)r.emplace_back(n,1);return r;}

vector<int> divisor(int n) { // 約数列挙 O(√n)
Vi r;for(int i=1;i*i<=n;i++){if(n%i==0){r.pb(i);if(i*i!=n)r.pb(n/i);}}
sort(ALL(r));return r;}

signed main() {
  cin.tie(0);cout.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(12);
  int n;
  cin >> n;
  if(n==2) {cout << 1 << endl;return 0;}
  int ans = 0;
  
  if(pp.size()==1){
    int ans = pp[0].SE;
    rep(i,1,v.size()){
      if(gcd(v[i],n)==1) ans++;
    }
    cout << ans << endl;
    return 0;
  }
  
  Vi v = divisor(n-1);
  VPii pp = facc(n);
  
  rep(i,0,pp.size()){
    //int now = mypow(pp[i].FI,pp[i].SE,INF);
    int now = pp[i].FI;
    rep(j,0,pp[i].SE){
      int nown = n;
      while(nown%now == 0 && nown >= now) nown /= now;
      if(nown%now == 1) {ans++;}
      now *= pp[i].SE;
    }
  }
  
  rep(i,1,v.size()){
    if(gcd(v[i],n)==1) ans++;
  }
  ans++;
  
  cout << ans << endl;
  return 0;
}

Compiler output:
a.cc:68:11: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   68 | void Vout(auto a){if(a.size()==0) cout<<"."<<endl;
      |           ^~~~
a.cc:70:11: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   70 | void Verr(auto a){if(a.size()==0) cerr<<"."<<endl;
      |           ^~~~
a.cc:72:12: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   72 | void VVout(auto a){if(a.size()==0)cout<<"."<<endl;
      |            ^~~~
a.cc:74:12: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   74 | void VVerr(auto a){if(a.size()==0)cerr<<"."<<endl;
      |            ^~~~
a.cc:76:12: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   76 | void VPout(auto a){if(a.size()==0)cout<<"."<<endl;
      |            ^~~~
a.cc:78:12: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   78 | void VPerr(auto a){if(a.size()==0)cerr<<"."<<endl;
      |            ^~~~
a.cc:90:12: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   90 | void press(auto &v){v.erase(unique(ALL(v)),v.end());} // 圧縮
      |            ^~~~
a.cc: In function 'int main()':
a.cc:126:6: error: 'pp' was not declared in this scope; did you mean 'mp'?
  126 |   if(pp.size()==1){
      |      ^~
      |      mp
a.cc:128:13: error: 'v' was not declared in this scope
  128 |     rep(i,1,v.size()){
      |             ^
a.cc:38:34: note: in definition of macro 'rep'
   38 | #define rep(i,a,b) for(int i=a;i<b;i++)
      |                                  ^