n=int(eval(input()))

print((n+sum(n//i*(i+n-n%i)//2for i in range(1,n))))
n=int(eval(input()))

print((n+sum(n//i*(n-n%i+i)>>1for i in range(1,n))))
n = int(eval(input()))
print((n + sum(n // i * (i + n - n % i) // 2 for i in range(1, n))))

n = int(eval(input()))
print((n + sum(n // i * (n - n % i + i) >> 1 for i in range(1, n))))

-print((n + sum(n // i * (i + n - n % i) // 2 for i in range(1, n)))) +print((n + sum(n // i * (n - n % i + i) >> 1 for i in range(1, n))))