#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int p,d,m,s;
    cin >> p >> d >> m >> s;
    
    vector<int> vals = {p};
    while ( vals[vals.size() - 1] - d > m ) {
        vals.push_back(vals[vals.size()-1]-d);
    }
    while ( vals.size() < 2e4 ) {
        vals.push_back(m);
    }
    for ( int i=1; i<vals.size(); ++i ) {
        vals[i] = vals[i] + vals[i-1];
    }
    
    //find the largest number less than or equal to our money.
    
    int pos = upper_bound(vals.begin(), vals.end(), s) - vals.begin();
    while ( vals[pos] > s ) {
        --pos;
    }
        
    cout << pos + 1<< endl;
    
    
    return 0;
}