if __name__ == "__main__":
    p, d, m, s = input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    count=0
    sum=0
    fl=p
    while(sum<=s):
        if fl<m:
            fl=m
        sum+=fl
        count+=1
        fl=fl-d
    print(count-1)