啊飒飒
#include<stdio.h>
int main()
{
int n;
scanf("%d",&n);
int i,j;
int sum1=0,sum2=0,sum;
for(i=1;i<=n;i++)
{
if(i%2==0)
{
sum1+=i;
}
else
sum2+=i;
}
sum = sum2-sum1;
printf("%d",sum);
}
int main()
{
int n;
scanf("%d",&n);
int i,j;
int sum1=0,sum2=0,sum;
for(i=1;i<=n;i++)
{
if(i%2==0)
{
sum1+=i;
}
else
sum2+=i;
}
sum = sum2-sum1;
printf("%d",sum);
}