Cod sursa(job #2039110)

Utilizator mircearoataMircea Roata Palade mircearoata Data 14 octombrie 2017 11:26:16
Problema Invers modular Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.83 kb
#include <iostream>
#include <fstream>

using namespace std;

ifstream in("inversmodular.in");
ofstream out("inversmodular.out");

long long expow(long long b, long long p, long long mod)
{
    long long pow=1;
    while(p!=1){
        if(p%2==0)
        {
            p=p/2;
            b=b*b%mod;
        }else{
            p=p-1;
            pow=pow*b%mod;
        }
    }
    b=b*pow%mod;
    return b%mod;
}

long long phi(long long n)
{
    long long nr=n;
    for(long long i = 2; i*i<=n;i++)
    {
        if(n%i==0)
        {
            while(n%i==0)
            {
                n/=i;
            }
            nr=(nr/i)*(i-1);
        }
    }
    if(n!=1)
        nr=(nr/n)*(n-1);
    return nr;
}


long long a,n;

int main()
{
    in>>a>>n;
    out<<expow(a,phi(n)-1,n);
    return 0;
}