  #include<bits/stdc++.h>
  using namespace std;
  using ll = long long;
  #define rep(i,f,n) for(ll i=(f); (i) < (n); i++)
  #define repe(i,f,n) for(ll i=(f); (i) <= (n); i++)
  #define repc(i,f,n) for(char i=(f); (i) <= (n); i++)
  #define PI 3.14159265358979323846264338327950ll
  #define debug(x) cout<<#x<<" :: "<<x<<"\n";
  #define debug2(x,y) cout<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n";
  #define debug3(x,y,z) cout<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\n";
  #define Pl pair<ll, ll>
  #define dvec vector<vector<ll>>
  #define OUT(x) cout << x << endl; return 0;
  //printf("%.10f\n")
  //cout << fixed << setprecision(10);
  template<class T> inline bool chmax(T& a, T b){if (a < b) { a = b; return true; } return false;}
  template<class T> inline bool chmaxe(T& a, T b){if (a <= b) { a = b; return true; } return false;}
  template<class T> inline bool chmin(T& a, T b){if (a > b) { a = b; return true; } return false;}
  const ll MOD = 1000000007ll;
  const ll INF = 1e+18;
  const int iINF = 1e9;
  const double EPS = 1e-8;

int
main()
{
  double A, B; cin >> A >> B;
  cout << (A / 100) * B << endl;

}
#include<bits/stdc++.h>
#include<cmath>
#define pb push_back
#define ld long double
#define mp make_pair
#define vl vector<ll> 
#define vd vector<double>
#define vld vector<long double>
#define ll long long int
#define pl pair<ll, ll>
#define all(a) a.begin(), a.end()
#define forr(i, n) for(ll i=0; i<n; i++) 
#define forr1(i, n) for(ll i=1; i<=n; i++)
using namespace std;
const ld PI =3.1415926535897923846;
const ll MOD = 1000000007;
const ll N=998244353;
ll power(ll x,ll n){ll res=1;while(n>0){if(n&1) res=res*x%MOD;x=x*x%MOD;n>>=1;}return res;}
ll modinverse(ll a){return power(a, MOD-2);}
void solve()
{
    ll x, y, a, b;
    cin>>x>>y>>a>>b;
    // check when it's optimal to use b instead of a
    // when b>=x
    ll ans=0;
    while(x<b/a)
    {
    	ans++;
    	x*=a;
    	if(x>=y)
    	{
    		cout<<ans-1<<endl;
    		return;
    	}
    }
    //x/=a;
    //ans--;
    ll rem=max((ll)0, y-x);
    ans+=((rem/b));
    if(rem%b==0)
    	ans--;
    cout<<ans<<endl;
}
int main()
{
	#ifndef ONLINE_JUDGE
        // for getting input from input.txt
        freopen("input.txt", "r", stdin);
        // for writing output to output.txt
        freopen("output.txt", "w", stdout);
    #endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll test=1;
    //cin>>test;
    while(test--)
    {
        solve();
    }
    cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n";
}