Cod sursa(job #2685196)

Utilizator SochuDarabaneanu Liviu Eugen Sochu Data 16 decembrie 2020 11:55:37
Problema Invers modular Scor 0
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.89 kb
#include <bits/stdc++.h>
//#pragma GCC optimize ("03")
#define FastIO ios_base::sync_with_stdio(false) , cin.tie(0) , cout.tie(0)
#define FILES freopen("inversmodular.in" , "r" , stdin) , freopen("inversmodular.out" , "w" , stdout)
#define int long long
#define uint unsigned long long
#define ld long double
#define eb emplace_back
#define pb push_back
#define qwerty1 first
#define qwerty2 second
#define qwerty3 -> first
#define qwerty4 -> second
#define umap unordered_map
#define uset unordered_set
#define pii pair < int , int >
#define pq priority_queue
#define dbg(x) cerr << #x << ": " << x << '\n'

namespace FastRead
{
    char buff[5000];int lg = 0 , p = 0;
    char nc()
    {
        if(lg == p){lg = fread(buff , 1 , 5000 , stdin);p = 0;if(!lg) return EOF;}
        return buff[p++];
    }
    template<class T>void read(T&x)
    {
        T sgn = 1; char c;while(!isdigit(c = nc()))if(c == '-')sgn = -1;
        x = c - '0';while(isdigit(c = nc()))x = x * 10 + c - '0';x *= sgn;
    }
}

using namespace FastRead;
using namespace std;

const int N = 1e5 + 10;
const int M = 1e9 + 7;
const ld PI = acos(-1);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int a , n;

int pw(int N , int p)
{
    int ans = 1;

    for( ; p ; p >>= 1 , N = N * N % n)
        if(p & 1)
            ans = ans * N % n;

    return ans;
}

int euclid(int A , int B , int &X , int &Y)
{
    if(B == 0)
    {
        X = 1;
        Y = 0;
        return A;
    }

    int X0 , Y0;
    int D = euclid(B , A % B , X0 , Y0);

    X = Y0;
    Y = X0 - A / B * Y0;

    return D;
}

int phi(int n)
{
    int X , Y;
    euclid(a , n , X , Y);

    if(X < 0)
        return X + n;

    return X;
}

signed main()
{
	#ifndef ONLINE_JUDGE
		FastIO , FILES;
	#endif

    cin >> a >> n;
    cout << pw(a , phi(n) - 1);

    return 0;
}