输入一个正整数n，Sn=1-2+3-4+5-6...+x*n; x=1或者-1，C语言编程

#include <stdio.h>

int main()
{
int n;
printf("请输入一个正整数n：");
scanf("%d", &n);
int sum = 0;
int x = 1;
for (int i = 1; i <= n; i++)
{
sum += i * x;
x = -x;
}
printf("Sn的值为：%d\n", sum);
return 0;
}