#includeint main(void){ int n,s=0,i; scanf("%d",&n); for(i=1;i<=n;i++) s+=i; printf("s=%d",s);}
int sum=0;scanf("%d",&n);for(int i=0;i{sum=sum+i;}printf("累计的数是:%d",sum);
int f(int n){ return (n * n + n) /2;}