#include <stdio.h>
const int u[3] = {1, -3, 2};
const int v[2] = {-2, 3};
int g(int n){
int i, sum = 0;
for (i = 1; i <= n; i++) sum += u[i % 3] * i;
return sum;
}
int main( ){
int n, i, sum = 0;
scanf("%d", &n);
for (i = 1; i <= n; i++) sum += v[i % 2] * g(i);
printf("%d\n", sum);
return 0;
} 输入：103输出：1
