#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll i ,j , n , q , m , t ,ans,ma,z,p,d,val,a1,a2,k,a3[200005] ,a4[2000050],vis[200005],m1,jj,b[500005],c[50];
vector<ll> v[200005],v1;
map<ll,ll> mp[500005];

int main()
{
   cin >> p >> d >> m >> i;

       while(p>m && i>=p)
       {
           ans++;
           i=i-p;
           p=p-d;
       }
    if(p<=m)
    ans=ans+i/m;


   cout<<ans;

    return 0;

}