//g++ 1.cpp -std=c++14 -O2 -I .
#include <bits/stdc++.h>
using namespace std;

#include <atcoder/all>
using namespace atcoder;

using ll = long long;
using ld = long double;

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vld = vector<ld>;
using vvld = vector<vld>;

#define fi first
#define se second
#define pb push_back
#define pq_big(T) priority_queue<T,vector<T>,less<T>>
#define pq_small(T) priority_queue<T,vector<T>,greater<T>>
#define all(a) a.begin(),a.end()
#define rep(i,start,end) for(ll i=start;i<(ll)(end);i++)
#define per(i,start,end) for(ll i=start;i>=(ll)(end);i--)

constexpr ll mod = 998244353;

//p*q行列aとr*s行列bの積(mod)
template <class X> vector<vector<X>> matmulti(const vector<vector<X>> &a,const vector<vector<X>> &b,X mod){
  int p=a.size(),q=a[0].size(),r=b.size(),s=b[0].size();
  if(q!=r){
    cout<<"WARNING : SIZE ERROR"<<endl;
  }
  vector<vector<X>> res(p,vector<X>(s,0));
  
  for(int i=0;i<p;i++){
    for(int j=0;j<s;j++){
      for(int k=0;k<q;k++){
        res[i][j]+=(a[i][k]%mod*b[k][j]%mod)%mod;
      }
      res[i][j]%=mod;
    }
  }
  return res;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  ll a,b,p,q;
  cin>>a>>b>>p>>q;

  if(b==0){
    if(a==0){
      cout<<2<<"\n";
      return 0;
    }

    //pow1[i] := A^i
    //pow2[i] := A^{10^5 i}
    ll pow1[110000],pow2[110000];
    pow1[0]=1,pow2[0]=1;
    map<ll,int> m;
    m[1]=0;

    rep(i,1,110000){
      pow1[i]=pow1[i-1]*a;
      pow1[i]%=mod;
      m[pow1[i]]=i;
    }
    rep(i,1,110000){
      pow2[i]=pow2[i-1]*pow1[100000];
      pow2[i]%=mod;
    }

    rep(i,0,110000){
      ll inv=inv_mod(pow2[i],mod);
      ll z=(p*inv)%mod;
      ll ans=-1;
      if(z==1){
        ans=100000*i;
      }
      else if(m[z]!=0){
        ans=100000*i+m[z];
      }

      if(ans>=2){
        cout<<ans<<"\n";
        return 0;
      }
    }
    
    cout<<"Failed"<<endl;
    return 0;
  }

  vvll m(2,vll(2)),e(2,vll(2)),start(2,vll(1)),end(2,vll(1));
  m[0][0]=a,m[0][1]=(mod-b)%mod,m[1][0]=1,m[1][1]=0;
  e[0][0]=1,e[0][1]=0,e[1][0]=0,e[1][1]=1;
  start[0][0]=2,start[1][0]=(a*inv_mod(b,mod))%mod;
  end[0][0]=p,end[1][0]=q;

  //pow1[i] := m^i
  //pow2[i] := m^{10^5 i}
  vector<vvll> pow1,pow2;
  pow1.emplace_back(e),pow2.emplace_back(e);

  rep(i,0,110000){
    pow1.emplace_back(matmulti(pow1[i],m,mod));
  }
  rep(i,0,110000){
    pow2.emplace_back(matmulti(pow2[i],pow1[100000],mod));
  }

  map<vvll,int> seen;
  map<vvll,int> val;
  rep(i,0,110000){
    auto x=matmulti(pow1[i],start,mod);
    seen[x]=1;
    val[x]=i;
  }

  rep(i,0,110000){
    //x=m^{10^5 i}
    //inv_x = x^-1
    vvll x=pow2[i];
    ll det=x[0][0]*x[1][1]-x[0][1]*x[1][0];
    det=((det%mod)+mod)%mod;
    ll inv_det=inv_mod(det,mod);

    vvll inv_x(2,vll(2));
    inv_x[0][0]=(inv_det*x[1][1])%mod,inv_x[0][1]=(inv_det*(mod-x[0][1]))%mod,inv_x[1][0]=(inv_det*(mod-x[1][0]))%mod,inv_x[1][1]=(inv_det*x[0][0])%mod;

    auto z=matmulti(inv_x,end,mod);

    ll ans=-1;
    if(seen[z]==1){
      ans=100000*i+val[z];
    }

    if(ans>=2){
      cout<<ans<<"\n";
      return 0;
    }
  }
}