#include <stdio.h>

int main() {

    int n;
    scanf("%d", &n);
    int total = 0;
    int term = 0; //用于存储当前项
    for (int i = 1; i <= n; i++) {
        term += i; //更新当前项
        total += term; //累加当前项
    }

    printf("%d\n", total);

    return 0;
}