Cod sursa(job #1971155)

Utilizator Vlad_lsc2008Lungu Vlad Vlad_lsc2008 Data 19 aprilie 2017 21:21:56
Problema Invers modular Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.63 kb
#include<cstdio>
#include<iostream>
#define ll long long
using namespace std;

ll n,a;

ll getphi(int nr)
{
    ll sol=nr,mod=nr;
    for(ll i=2;i*i<=nr;i++)
        if(nr%i==0)
        {
            while(nr%i==0) nr/=i;
            sol=sol/i*(i-1)%mod;
        }
    if(nr!=1) sol=sol/nr*(nr-1)%mod;
    return sol;
}

int main()
{
    freopen("inversmodular.in","r",stdin);
    freopen("inversmodular.out","w",stdout);
    scanf("%lld%lld",&a,&n);
    ll p=getphi(n)-1;
    ll sol=1;
    for(ll i=1; i<=p; i<<=1)
    {
        if( i&p ) sol=sol*a%n;
        a=a*a%n;
    }
    cout<<sol<<'\n';
    return 0;
}