## https://yukicoder.me/problems/no/1514

import math

def main():
    N = int(input())

    sqrt_array = []
    x = 1
    while x ** 2 <= N:
        sqrt_array.append(x ** 2)
        x += 1
    
    answer = 0
    finished = [False] * (N + 1)
    index = len(sqrt_array) - 1
    for j in range(1, N + 1): 
        if finished[j]:
            continue

        while index >= 0 and j * sqrt_array[index] > N:
            index -= 1

        if index >= 0:        
            answer += (index + 1) ** 2
            x = j
            for i in range(index + 1):
                finished[x * sqrt_array[i]] = True
    
    print(answer)





                





    
        















if __name__ == "__main__":
    main()