---

import sys
import math

def solve():
    
    try:
        input_data = sys.stdin.read().split()
        if not input_data:
            return
        
        v = int(input_data[0])
        a = int(input_data[1])
        b = int(input_data[2])
        n = int(input_data[3])
        
       
        count_in = n // a
        
       
        count_out = n // b
        
        
        result = v + count_in - count_out
        
        print(result)
        
    except Exception as e:
       
        pass

if __name__ == "__main__":
    solve()