Cod sursa(job #1290580)

Utilizator Al3ks1002Alex Cociorva Al3ks1002 Data 11 decembrie 2014 15:20:23
Problema Invers modular Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.12 kb
#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>

using namespace std;

ll a, n, N, phi;

ll lgpow(ll a, ll b)
{
    ll r = 1;
    for(ll i = 1; i <= b; i <<= 1)
    {
        if(i & b) r = (r * a) % N;
        a = (a * a) % N;
    }
    return r;
}

int main()
{
    freopen("inversmodular.in", "r", stdin);
    freopen("inversmodular.out", "w", stdout);

    scanf("%lld%lld", &a, &n);
    N = n;

    phi = 1;
    for(int i = 2; i * i <= n; i++)
        if(n % i == 0)
        {
            while(n % i == 0)
            {
                phi *= i;
                n /= i;
            }
            phi /= i;
            phi *= (i - 1);
        }
    if(n > 1) phi *= (n - 1);

    printf("%lld\n", lgpow(a, phi - 1));

    return 0;
}