C语言求1-2+3-4+5..-100的和

#include 
#include 

int main(){
    int sum,k,i;
    sum=0,k=1;
    for (i=1; i<=100; i++) {
        sum=sum+k*i;
        k=-1*k;
    }
    printf("1-2+3-4+5..-100的和为：%dn",sum);
    return 0;
}