#include<bits/stdc++.h>

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


#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 1000005
#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 h1 47
#define h2 101mp
#define mod5 1024523
#define endl '\n'
#define paa pair<pair<int,int>,int > 

using namespace std;
int main()
{
	
//	 #ifndef ONLINE_JUDGE
//     freopen("in.txt","r",stdin);
//     freopen("out.txt","w",stdout);
//     #endif

	int n,a,b,c,coun=0,sum=0;
	cin>>n>>a>>b>>c;
	sum=0;
	while(1)
	{
		sum+=n;
		
		if(sum>=c)
		break;
		coun++;
		
		n=n-a;
		if(n<b)
		n=b;
	}
	
	if(sum==c)
	coun++;
	cout<<coun<<endl;
	
}