Cod sursa(job #1826958)

Utilizator tanasaradutanasaradu tanasaradu Data 11 decembrie 2016 11:11:50
Problema Invers modular Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.85 kb
#include <iostream>
#include<fstream>
using namespace std;
ifstream fin("inversmodular.in");
ofstream fout("inversmodular.out");
int a,n;
void Citire()
{
    fin>>a>>n;
}
inline int Fi(int x)
{
    int d=2,fi;
    fi=n;
    while(x>1 && d*d<=x)
    {
        if(x%d==0)
        {
            fi=(fi/d)*(d-1);
            while(x%d==0)
                x/=d;
        }
        d++;
    }
    if(x>1)fi=(fi/x)*(x-1);
    return fi;
}
inline int Putere(int x,int y)
{
    int sol=1;
    while(y)
    {
        if(y%2==1)
        {
            sol=(1LL*sol*x)%n;
            y--;
        }
        y/=2;
        x=(1LL*x*x)%n;
    }
    return sol;
}
int main()
{
    int x;
    Citire();
    ///Mica teorema a lui Fermat:a^(fi(n))%n==1 ,(a,n)=1
    x=Fi(n)-1;
    fout<<Putere(a,x)<<"\n";
    fin.close();
    fout.close();
}