Cod sursa(job #228198)

Utilizator filipbFilip Cristian Buruiana filipb Data 6 decembrie 2008 18:36:23
Problema Invers modular Scor Ascuns
Compilator cpp Status done
Runda Marime 0.71 kb
#include <stdio.h>
#include <assert.h>

#define ll long long

int A, N;

void gcd(ll &x, ll &y, int &d, int a, int b)  
{  
     if (!b)  
         d = a, x = 1, y = 0;  
     else  
     {             
         gcd(x, y, d, b, a % b);
         ll aux = x;
         x = y;
         y = aux - y * (a / b);
     }
}

int main()
{
    ll inv = 0, ins;
    int d;
    
    freopen("inversmodular.in", "r", stdin);
    freopen("inversmodular.out", "w", stdout);
    
    scanf("%d %d", &A, &N);
    assert(1 <= A && A < N && N <= 2000000000);
    gcd(inv, ins, d, A, N);
    assert(d == 1);

    if (inv <= 0)
       inv += N - inv % N;
       
    printf("%lld\n", inv);
      
    return 0;
}