#include <bits/stdc++.h>

#define pii pair<int,int>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pf push_front
#define pb2 pop_back
#define pf2 pop_front
#define rep(k,i,j) for(int k = (int)i;k<(int)j;k++)
#define repd(k,i,j) for(int k = (int)i;k>=(int)j;k--)
#define ll long long
#define line puts("")
#define ALL(a) a.begin(),a.end()
#define vi vector<int> 
#define SIZE(a) a.size()

const int INF = 1e9+7;
const ll INFLL = 1e17;
const double EPS = 1e-6;

using namespace std;

int main(){
    int p,d,m,s;
    
    cin>>p>>d>>m>>s;
    int ret = 0;
    while(s-p>=0){
        s-=p;ret++;
        p-=d;
        if(p<=m)p = m;
    }
    cout<<ret<<endl;
    
}