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Cod sursa(job #533099)
#include <algorithm>
#include <fstream>
using namespace std;
const char Input[] = "inversmodular.in";
const char Output[] = "inversmodular.out";
long long int A, N;
long long int Phi( long long int x ) {
int i;
long long int aux;
aux = N;
for( i = 2; i * i <= N; ++i )
if( N % i == 0 ) {
aux = aux / i * (i - 1);
while( N % i == 0 )
N /= i;
}
if( N > 1 )
aux = aux / N * (N - 1);
return aux;
}
long long int Pow( int x, int p ) {
int i;
long long int aux, xxx;
aux = x;
xxx = 1;
for( i = 0; (1 << i) <= p; ++i ) {
if( (1 << i) & x )
xxx = (xxx * aux) % N;
aux = (aux * aux) % N;
}
return xxx;
}
int main() {
ifstream fin( Input );
ofstream fout( Output );
fin >> A >> N;
fout << Pow( A, Phi( N ) - 1 );
fin.close();
fout.close();
return 0;
}