Cod sursa(job #2685106)

Utilizator pielevladutPiele Vladut Stefan pielevladut Data 15 decembrie 2020 23:10:30
Problema Invers modular Scor 0
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.79 kb
#include<bits/stdc++.h>
using namespace std;
ifstream fin("inversmodular.in");
ofstream fout("inversmodular.out");
int n,a,phi;
int phi_euler(int n)
{
    int nn = n, ans = n;
    for(int i = 2; i * i <= n; i ++)
    {
        if(nn % i == 0)
        {
            ans *= (i-1);
            ans /= n;
            while(nn % i != 0)
                nn /= i;
        }
    }
    if(nn != 1)
    {
        ans *= (nn-1);
        ans /= n;
    }
    return ans;
}
int lgput(int base,int exp)
{
    long long i;
    int aux=base,ans=1;
    for(i=1; i<=exp; i*=2)
    {
        if(i&exp)
            ans=(1LL*ans*aux)%n;
        aux=(1LL*aux*aux)%n;
    }
    return ans;
}

int main()
{
    fin>>a>>n;
    phi=phi_euler(n);
    fout<<lgput(a,phi-1);
    return 0;
}