#!/bin/ruby

def howManyGames(p, d, m, s)
    count = 0
    if(p <= s)
        s -= p
        count += 1
    else
        return 0
    end
    
    cp = p - d
    
    while(cp <= s && cp >= m)
        s -= cp
        cp -= d
        count += 1
    end
    

    
    if s > 0 && cp <= m
        count += s / m
    end
    
    count
    
end

p, d, m, s = gets.strip.split(' ')
p = p.to_i
d = d.to_i
m = m.to_i
s = s.to_i
answer = howManyGames(p, d, m, s)
puts answer