Cod sursa(job #2434057)

Utilizator blotucosmincosmin blotucosmin Data 30 iunie 2019 15:23:13
Problema Invers modular Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.79 kb
#include<fstream>
#define ll long long
using namespace std;
ifstream fin("inversmodular.in");
ofstream fout("inversmodular.out");
ll a,n,MOD;
ll lgnp(ll n, ll p)
{
    n=n%MOD;
    ll r=1;
    while(p)
    {
        if(p%2==1) r=(1LL*r*n)%MOD;
        n=(n*n*1LL)%MOD;
        p/=2;
    }
    return r%MOD;
}
ll phi(ll n)
{
    int d=2,fm;
    ll nr=1;
    do
    {
        fm=0;
        while(n%d==0)
        {
            n/=d;
            fm++;
        }
        if(fm>0) nr*=(d-1)*lgnp(d,fm-1);
        d++;
        if(d*d>n&&n>1)
        {
            nr=nr*(n-1);
            n=1;
        }
    }
    while(n>1);
    return nr;
}
int main()
{
    fin>>a>>n;
    MOD=n;
    fout<<lgnp(a,phi(n)-1);
    //FORMULA: (A ^ (phi(n)-1) ) % MOD;
    return 0;
}