View Code of Problem 18

#include <stdio.h>
int main() {
    int n,sum,k;
    while(scanf("%d",&n)!=EOF){
        k=0;
        sum=0;
        for(int i=1;i<=n;i++){//注意顺序，先加再判定
            sum=sum+k;
            if(i%2==0){  //遇到偶数就加一次
                k++;
            }
        }
        printf("%d\n",sum);
    }
	return 0;
}