#include<iostream>
using namespace std;
int main()
{
    int p, d, m, s, i;
    cin >> p >> d >> m >> s;
    int count = 1, sum = 0, diff = 0, rem = 0;
    if(p>0)
    {
        diff = p-d;
        sum = p + diff;
        count++;
    }
    for(i=0;;i++)
    {     
        
        if(diff<=m)
                {
                    rem = m%diff;
                    diff = diff + rem;
                    sum = sum + diff;
                    if(sum>s)
                    {
                        sum = sum - diff;
                        break;
                    }
                    count++;
                    
                }
        diff = diff - d;
        sum = sum + diff;
        count++;
    }
    cout << count;
}