#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <list>
#include <utility>
#include <iterator>
#include <map>
#include <stack>
#include <queue>
#include <set>
#include <deque>
#include <bitset>
#include <complex>
#include <iomanip>
#include <assert.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>

//#include <unordered_set>
#include <unordered_map>

#define cint(a) scanf("%d",&a)
#define cflt(a) scanf("%f",&a)
#define cstr(a) scanf("%s",&a)
#define cchr(a) scanf("%c",&a)
#define cli(a) scanf("%ld",&a)
#define cdob(a) scanf("%lf",&a)
#define mod 1000000007
#define mod2 1000000009
#define mod1 1432344041
#define ima 1000000004
#define imi -1000000004
#define llma 1000000000000000004
#define llmi -1000000000000000004
#define lp(i,n) for(i=0;i<n;i++)
#define li(i,n) for(i=n-1;i>=0;i--)
#define ll long long int
#define ld long double
#define f first
#define s second
#define pa pair<ll,ll>
#define pad pair<double ,double>
#define pai pair<int,int>
#define pal pair<int,ll>
#define pai3 pair< int , pai >
#define mp make_pair
#define nn 100005
#define pi 3.1415926535898
#define inf 1e15
#define diff 1e-7
#define it ::iterator
#define pb push_back
#define sync ios::sync_with_stdio(false);cout.tie(0);cin.tie(0);
#define lc(a) 2*a+1
#define rc(a) 2*a+2
#define endl "\n"
#define h1 47
#define h2 101mp
#define mod5 1024523
#define N 3000005
#define lgN 24


using namespace std;

typedef complex<double> base;
typedef priority_queue<int, vector<int>, greater<int> > min_pq;
typedef priority_queue<pai3, vector<pai3>, greater<pai3> > min_pq1;
typedef priority_queue<pai, vector<pai > > pq;

ll x,y;
ll gcd(ll a,ll b){if(a==0) {x=0,y=1; return b;}ll gc=gcd(b%a,a);ll temp;temp=x;x=y-(b/a)*temp;y=temp;return gc;}//y is the inverse and a is modulus

ll po(ll a, ll x, ll m){ if(x==0){return 1;}ll ans=1, k=1;  while(k<=x) {if(x&k){ans=((ans*a)%m);} k<<=1; a*=a;a%=m; }return ans; } //(a^x)%m




int main()
{
    sync
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int ans=0;
    for(int i=0;s>0;i++)
    {
        s-=p;
        if(s>=0)
            ans++;
        p-=d;
        if(p<m)
            p=m;
    }
    cout<<ans;
}