#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
#define fr(a,b) for(ll i=a;i<b;i++)
#define pb push_back
#define mod 1000000007
#define K 1000000007

int main(){
  ios::sync_with_stdio(false);
  cin.tie(NULL);

  ll p,d,m,s;
  cin>>p>>d>>m>>s;

  ll as=0,al=s,cnt=0,ip=p;
  while(al>0){
    if(ip<=al){
      cnt++;
      al-=ip;
      if(ip-d>=m) ip-=d;
      else ip=m;
    }
    else break;
  }

  cout<<cnt;

  return 0;
}