/*
ID: meirhan2
PROG: beads
LANG: C++11
*/
#include<bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define popb pop_back()
#define sz size()
#define y0 luboi
#define y1 luboi1
#define y2 luboi2
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
typedef long long ll;
///////////////////////////////////////////

int m,p,d,s;
int ans=0;
int sum=0;
int main(){speed
    cin>>p>>d>>m>>s;
    //if(p>m) ans++;
    while(p>m){
        ans++;
        sum+=p;
        if(sum>=s){
            ans--;
            break;
        }
        p-=d;
        if(p<=m) break;
        //cout<<p<<endl;
    }
    //cout<<p<<endl;
    while(sum<=s){
        sum+=m;
        if(sum>s) break;
        ans++;
    }
    cout<<ans;
}