#include <bits/stdc++.h>
#define mem( a , b ) memset( a , b , sizeof( a ) )
using namespace std;
int _I(){ int x; scanf("%d", &x ); return x; }
struct node{
    int h , a , s;
    node(){}
    node ( int x ,int y ,int z )
    {
        h = x;
        a = y;
        s = z;
    }
};
void solve()
{
        int m , p , d , s;
        p = _I();
        d = _I();
        m = _I();
        s = _I();
        int ans = 0;
        int sum = 0;
        while( s >= sum  )
        {
               if( p <= m ){
                        p = m;
                        d = 0;
               }
               sum += p;
               if( sum > s ) break;
               p -= d;
               ans++;
        }
        cout<<ans<<"\n";
}
int main()
{
    //freopen( "input.txt" , "r" , stdin );
    //int t = _I();
    //while( 1 )
        solve();
    return 0;
}