import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    ctr=0
    while s>0:
        s-=max(p-(ctr*d), m)
        
        if s>=0:
            ctr+=1
        else:
            return ctr
        
    return ctr
if __name__ == "__main__":
    p, d, m, s = raw_input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print answer