#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define sz size()
#define forn(i,m) for(int i=0;i<(int)(m);i++)
#define fornn(i,n,m) for(int i=n;i<(int)(m);i++)
#define forb(i,n,m) for(int i=n;i>=(int)(m);i--)
#define forit(it,c) for(__typeof(c.begin()) it=c.begin();it!=c.end();++it)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define eprintf(...) fprintf(stderr, __VA_ARGS__),fflush(stderr)
#define pw(x) (1LL<<(x))
#define DBGV(vari) cout << #vari<< " = "<< (vari) <<endl;
#define debug(x)   {cerr <<#x<<" = " <<x<<"\n"; }
#define debug2(x, y)       {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<"\n";}
#define debug3(x, y, z)    {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<", "<<#z<<" = "<<z<<"\n";}
#define debug4(x, y, z, w) {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<", "<<#z<<" = "<<z<<", "<<#w << " = " <<w <<"\n";}

typedef stringstream sstr;
typedef pair<int, int> pii;
typedef vector<pii> vpii;
typedef vector<string> vs;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<vector<int> > vvi;
typedef long long ll;
typedef long double ld;
typedef vector<ll> vll;
typedef pair<double,double> pdd;
typedef pair<long,long> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;

inline int nextint(){ int x; scanf("%d",&x);   return x; }
inline ll  nextll() { ll  x; scanf("%lld",&x); return x; }

#define gc getchar
template <typename T> void scanint(T &x) {
T c = gc(); while(((c < 48) || (c > 57)) && (c!='-')) c = gc();
bool neg = false; if(c == '-') {neg = true; c = gc();} x = 0; for(;c < 48 || c > 57;c=gc());
for(;c > 47 && c < 58;c=gc()) x = (x*10) + (c - 48); if(neg) x = -x;
}
// variadics
template<typename T >T min_ ( T a , T b ) { return a > b ? b : a ; }
template < typename T ,  typename... Ts > T min_( T first , Ts... last ){ return  min_(first, min_(last...)); }
template<typename T >T max_ ( T a , T b ) { return a > b ? b : a ; }
template < typename T ,  typename... Ts > T max_( T first , Ts... last ){ return  max_(first, max_(last...)); }

// lambda exp auto  square = [](int inp) { return inp * inp; } ;

template<class T, class S> std::ostream& operator<<(std::ostream &os, const std::pair<T, S> &t) {
os<<"("<<t.first<<", "<<t.second<<")";
return os;
}
template<typename T> ostream& operator<< (ostream& out, const vector<T>& v) {
    out << "["; size_t last = v.size() - 1; for(size_t i = 0; i < v.size(); ++i) {
    out << v[i]; if (i != last) out << ", "; } out << "]"; return out;
}
template<typename T> ostream& operator<< (ostream& out, const set<T>& v) {
    out << "{"; auto last = v.end(); for(auto i = v.begin(); i != last;) {
    out << *i; if (++i != last) out << ", "; } out << "}"; return out;
}
template<typename T, typename VAL> ostream& operator<< (ostream& out, const map<T,VAL>& v) {
    out << "{"; auto last = v.end(); for(auto i = v.begin(); i != last;) {
    out << *i; if (++i != last) out << ", "; } out << "}"; return out;
}

template <typename Arg, typename... Args>
void doPrint(std::ostream& out, Arg&& arg, Args&&... args)
{
    out<<"<< ";
    out << std::forward<Arg>(arg);
    using expander = int[];
    (void)expander{0, (void(out << ", " << std::forward<Args>(args)),0)...};
    out<<" >>\n";
}

ll pwr(ll base, ll p, ll mod){
ll ans = 1; while(p) { if(p&1) ans=(ans*base)%mod; base=(base*base)%mod; p/=2; } return ans;
}
ll gcd(ll a, ll b) {  return b == 0 ? a : gcd(b,a%b); }
ll lcm(ll a, ll b) {  return a*(b/gcd(a,b)); }

const long double PI = (long double)(3.1415926535897932384626433832795);
const ll  mx_ll   = numeric_limits<ll> :: max();
const int mx_int  = numeric_limits<int> :: max();
const int mod = 1e9+7;
const int oo = 0x3f3f3f3f;
const ll  OO = 0x3f3f3f3f3f3f3f3fll;
const double eps = 1e-9;

/*************************************************************************/

const int maxn=100123;


void solve(){
}

/*************************************************************************/

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

/*************************************************************************/