n=int(input())
if n%2!=0:
    i=0
    s=0
    while i<n:
        s+=i
        i+=2
    print(s)
if n%2==0:
    i=1
    s=0
    for i in range(1,n+1):
        if n%i==0:
            s+=i
            i+=1       
    print(s)
    
    
    
    
/**************************************************************
	Problem: 1060
	User: admin
	Language: Python
	Result: Accepted
	Time:94 ms
	Memory:34480 kb
****************************************************************/