#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
const double pi = acos(-1);
const int maxn = 2e6 + 10;
const double eps = 1e-8;
const ll mod = 1e9 + 7;
const ull base = 131;
const ull mod1 = 1e9 + 9;
const ull mod2 = 1610612741;

ll x, y, a, b;

int main() {
    scanf("%lld%lld%lld%lld", &x, &y, &a, &b);
    ll ans = 0;
    ll k = b/(a-1);
    while (x <= k && x*a < y) x *= a, ++ans;
    if (x < y) ans += (y-x-1)/b;
    printf("%lld\n", ans);


    return 0;
}



#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (long long i = 0; i < (long long)(n); i++)
typedef long long  ll;
const ll mod=1e9+7;
typedef pair<int,int> P;
const int INF=1<<29;
int main(){
    double a,b;
    cin>>a>>b;
    cout<<fixed<<setprecision(10);
    cout<<a*b/100<<endl;
}