/*input
3
2
3
6
*/

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

#define fill(a,val) memset(a, (val), sizeof a)
#define pb push_back
#define lli long long int
#define scantype int
#define endl "\n"
#define unique(x) x.erase(unique(x.begin(),x.end()), x.end())
#define sort_f(x)  sort(x.begin(),x.end());
#define sort_r(x)  sort(x.rbegin(),x.rend());

lli MOD  = 1000000007;
lli inf = 1e15;

void scan(scantype &x);
lli powermod(lli _a,lli _b,lli _m){lli _r=1;while(_b){if(_b%2==1)_r=(_r*_a)%_m;_b/=2;_a=(_a*_a)%_m;}return _r;}
lli string_to_number(string s){lli x=0; stringstream convert(s); convert>>x; return x;}
lli add(lli a,lli b){lli x = (a+b)%MOD; return x; }
lli mul(lli a,lli b){lli x = (a*b)%MOD; return x; }
lli sub(lli a,lli b){lli x = (a-b+MOD)%MOD; return x; }
lli divi(lli a,lli b){lli x = a;lli y = powermod(b,MOD-2,MOD);lli res = (x*y)%MOD;return res;}

#define N 200003

long  divisors(long x) {
    long limit = x;
    long numberOfDivisors = 0;

    if (x == 1) return 1;

    for (long i = 1; i < limit; ++i) {
        if (x % i == 0) {
            limit = x / i;
            if (limit != i) {
                numberOfDivisors++;
            }
            numberOfDivisors++;
        }
        if(numberOfDivisors>=4)
        {
            break;
        }
    }

    return numberOfDivisors;
}
 bool isPrime(long n)
{
   
    if (n <= 1)  return false;
    if (n <= 3)  return true;
    if (n%2 == 0 || n%3 == 0) return false;
 
    for (long i=5; i*i<=n; i=i+6)
        if (n%i == 0 || n%(i+2) == 0)
           return false;
 
    return true;
}
int main()
{

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    long p,d,m,s;
    cin>>p>>d>>m>>s;
    long countm=0;
    if(p>s)
    {
        cout<<"0";
        return 0;
    }
    for(int i=0;i<s;i++)
    {
        s-=p;
        countm++;
        if(p-d>m)
        {
          p-=d;  
        }
        else
        {
            break;
        }
        
        
    }
    countm+=(s/m);
    cout<<countm;
   
    return 0;
}