#include <bits/stdc++.h>
#define ff first
#define ss second
#define ALL(x) (x).begin(), (x).end()
#define DV(x) cerr << ">> " << #x << " = >" << x << "<" << endl
#define F(i, a, b) for ( int i = (a); i < (b); ++i )
#define FD(i, a, b) for ( int i = (a); i >= (b); --i )
#define PB push_back
#define R1(a) scanf( "%d", &a )
#define R2(a, b) scanf( "%d%d", &a, &b )
#define R3(a, b, c) scanf( "%d%d%d", &a, &b, &c )
using namespace std;

#define D(args...) dbg,args; cerr<<endl;
struct debugger {
    template<typename T>
    debugger & operator,(const T & v) {
        cerr << ">" << v << "< ";
        return *this;
    }
} dbg;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vi> Matrix;

const int INF = 1e9 + 7;
const double PI = acos(-1);
const double EPS = 1e-9;

template <class T1, class T2> ostream & operator<<(ostream & os, const pair<T1,T2> & p) {
    return os << p.ff << " " << p.ss;
}

template <class T> ostream & operator<<(ostream & os, const vector<T> & v) {
    F(i,0,v.size())
    {
        if (i)
            os << " ";
        os << v[i];
    }
    return os;
}

int main()
{
    ios::sync_with_stdio(0);
    int p, d, m, s, res = 0;
    cin >> p >> d >> m >> s;
    while (s >= p) {
        s -= p;
        ++res;
        p = max( p-d, m );
    }
    cout << res << endl;
    return 0;
}