每日一九度之 题目1063：整数和

//Asimple
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cctype>
#include <cstdlib>
#include <stack>
#include <cmath>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <limits.h>
#define INF 0x7fffffff
using namespace std;
const int maxn = 105;
typedef long long ll;
int n, sum;
 
int main(){
    while( ~scanf("%d",&n) ){
        printf("%d\n",n>0?3*n*(n+1)/2:3*n*(1-n)/2);
    }
    return 0;
}