#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    count=0
    countt=0
    z=p
    i=0
    while(p<s):
        
        temp1=z-d
        p=p+(z-(i*d))
        i=i+1
        
        
        
        
        count+=1
        if(temp1<=m):
            while(p<s):
                
                temp1=6
                p=p+temp1
                countt+=1
    return(count+countt+2)       
        
            
        
    # Return the number of games you can buy

if __name__ == "__main__":
    p, d, m, s = input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print(answer)