Cod sursa(job #2624709)

Utilizator Sho10Andrei Alexandru Sho10 Data 5 iunie 2020 10:32:13
Problema Invers modular Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.09 kb
#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define sz size
#define f first
#define s second
#define pb push_back
#define er erase
#define in insert
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000000007
#define modul 998244353
#define PI 3.14159265359
#define CODE_START  ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll a,n,inv=0;
ll pw(ll a,ll b){
    if(b==0) return 1;
    ll x=pw(a,b/2);
    if(b%2==1){
            return (((x*x)%n)*a)%n;
    }else return (x*x)%n;
}
ll phi(ll x){
ll ans=x;
for(ll i=2;i*i<=n;i++)
{
    if(x%i==0){
        ans=(ans/i);
     ans=ans*(i-1LL);
     while(x%i==0){
        x=x/i;
     }
     }
}
if(x>1){
    ans=ans/x;
    ans=ans*(x-1LL);
}
return ans;
}
int32_t main(){
CODE_START;
ifstream cin("inversmodular.in");
ofstream cout("inversmodular.out");
cin>>a>>n;
phi(n);
cout<<pw(a,phi(n)-1LL)%n<<endl;
}