#include <bits/stdc++.h>
using namespace std;
const int SQRT = 100000;
const long long MOD = 998244353;
long long modpow(long long a, long long b){
	long long ans = 1;
	while (b > 0){
		if (b % 2 == 1){
			ans *= a;
			ans %= MOD;
		}
		a *= a;
		a %= MOD;
		b /= 2;
	}
	return ans;
}
long long modinv(long long a){
	return modpow(a, MOD - 2);
}
vector<vector<long long>> matmul(vector<vector<long long>> A, vector<vector<long long>> B){
	int N = A.size();
	vector<vector<long long>> ans(N, vector<long long>(N, 0));
	for (int i = 0; i < N; i++){
		for (int j = 0; j < N; j++){
			for (int k = 0; k < N; k++){
				ans[i][k] += A[i][j] * B[j][k];
				ans[i][k] %= MOD;
			}
		}
	}
	return ans;
}
vector<vector<long long>> matexp(vector<vector<long long>> A, long long b){
	int N = A.size();
	vector<vector<long long>> ans(N, vector<long long>(N, 0));
	for (int i = 0; i < N; i++){
		ans[i][i] = 1;
	}
	while (b > 0){
		if (b % 2 == 1){
			ans = matmul(ans, A);
		}
		A = matmul(A, A);
		b /= 2;
	}
	return ans;
}
int main(){
  int A, B, P, Q;
  cin >> A >> B >> P >> Q;
  if (B == 0){
    if (A == 0){
      cout << 2 << endl;
    } else {
      vector<long long> a(SQRT);
      a[0] = P;
      for (int i = 0; i < SQRT - 1; i++){
        a[i + 1] = a[i] * modinv(A) % MOD;
      }
      map<long long, int> mp;
      for (int i = 0; i < SQRT; i++){
        mp[a[i]] = i;
      }
      long long A2 = modpow(A, SQRT);
      long long X = A * A % MOD, N = 2;
      while (true){
        if (mp.count(X) == 1){
          cout << N + mp[X] << endl;
          break;
        }
        X *= A2;
        X %= MOD;
        N += SQRT;
      }
    }
  } else {
    vector<vector<long long>> C = {{A, MOD - B}, {1, 0}};
    vector<vector<long long>> Cinv = {{0, 1}, {(MOD - 1) * modinv(B) % MOD, A * modinv(B) % MOD}};
    vector<pair<long long, long long>> a(SQRT);
    vector<vector<long long>> tmp = {{1, 0}, {0, 1}};
    a[0] = make_pair(P, Q);
    for (int i = 0; i < SQRT - 1; i++){
      tmp = matmul(tmp, Cinv);
      a[i + 1] = make_pair((tmp[0][0] * P + tmp[0][1] * Q) % MOD, (tmp[1][0] * P + tmp[1][1] * Q) % MOD);
    }
    map<pair<long long, long long>, int> mp;
    for (int i = 0; i < SQRT; i++){
      mp[a[i]] = i;
    }
    vector<vector<long long>> C2 = matexp(C, SQRT);
    long long X = (A * A - B * 2 + MOD % MOD) % MOD, Y = A;
    long long N = 2;
    while (true){
      if (mp.count(make_pair(X, Y)) == 1){
        cout << N + mp[make_pair(X, Y)] << endl;
        break;
      }
      long long X2 = (C2[0][0] * X + C2[0][1] * Y) % MOD;
      long long Y2 = (C2[1][0] * X + C2[1][1] * Y) % MOD;
      X = X2;
      Y = Y2;
      N += SQRT;
    }
  }
}