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Cod sursa(job #226484)
#include <cstdio>
using namespace std;
inline int gcd(int A, int B, int &X, int &Y)
{
if (B == 0)
{
X = 1;
Y = 0;
return A;
}
int D, X0, Y0;
D = gcd(B, A % B, X0, Y0);
// X0 * B + Y0 * (A - (A / B) * B)
// X0 * B + Y0 * A - Y0 * B * (A / B)
X = Y0;
Y = X0 - Y0 * (A / B);
return D;
}
int main()
{
freopen("inversmodular.in", "rt", stdin);
freopen("inversmodular.out", "wt", stdout);
int N, P;
scanf("%d %d", &N, &P);
int D, X, Y;
D = gcd(N, P, X, Y);
// N * X + P * Y == 1
// N * X == 1 (mod P)
printf("%d\n", X);
return 0;
}