#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
N = int(readline())

# %%
if N == 1:
    print(0)
else:
    print((N * N * N + 3 * N * N + 5 * N - 3) // 6)