Cod sursa(job #2281415)

Utilizator borzaalexAlexandru Borza borzaalex Data 12 noiembrie 2018 10:53:06
Problema Invers modular Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.71 kb
#include <bits/stdc++.h>
using namespace std;
long long int a,n,phideN;

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

int main()
{
    fin>>a>>n;
    phideN=1;
    long long int d=2;
    long long int m=n;
    while(m>1)
    {
        if(d*d>m) d=m;

        if(m%d==0)
        {
           while(m%d==0) m/=d,phideN*=d;

           phideN=phideN/d*(d-1);
        }
        if(d==2) d=3;
        else d+=2;

    }

    long long int sol=1;
    long long int p=phideN-1;
    while(p>0)
    {
        if(p%2==1)
        {
            sol=(sol*a)%n;
            p--;
        }
        a=(a*a)%n;
        p/=2;

    }
    fout<<sol%n;
    return 0;

}