Cod sursa(job #2039444)

Utilizator Iorgus08Iorgus Serghei Cicala Iorgus08 Data 14 octombrie 2017 16:07:11
Problema Invers modular Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.86 kb
#include <bits/stdc++.h>

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