Cod sursa(job #1653739)

Utilizator andrew_assassin789Andrei Manea andrew_assassin789 Data 16 martie 2016 15:33:38
Problema Invers modular Scor 10
Compilator cpp Status done
Runda Arhiva educationala Marime 0.59 kb
#include <fstream>
#define w 2000001
using namespace std;
unsigned int phi[w];
long long po(long long a,long long b)
{
    long long rez=1;
    while (b)
    {
        if (b%2) rez*=a;
        a*=a;
        b/=2;
    }
    return rez;
}
int main()
{
    ifstream f("inversmodular.in");
    ofstream g("inversmodular.out");
    int i,j,n,a;
    f>>a>>n;
    for (i=2;i<=n/2;i++)
    {
        phi[2*i]++;
        for (j=3*i;j<=n;j+=i)
            phi[j]+=phi[j-i];
    }
    long long x=po(a,n-2-phi[n]);
    g<<x%n<<'\n';
    f.close();
    g.close();
    return 0;
}