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

typedef long long ll;
typedef pair<int,int> pii;

ll MOD = 1e9 + 7;

int main(){

	ios::sync_with_stdio(false);
    cin.tie(NULL);

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

    int count1 = 0;
    int curr = p;
    while(s>0){
    	if(s>=curr){
    		s-=curr;
    		count1++;
    		curr = max(curr-d,m);
    	}
    	else{
    		break;
    	}
    }

    cout<<count1<<endl;

	return 0;
}