求1+2+3+n后的结果

class Sum{public:Sum(){  num++;sum+=num;}int getSum(){return sum;}static int num;static int sum;}int Sum::num=0;int Sum::sum=0;void main(){  Sum *p=new Sum[100];   delete []p;cout<<Sum::getSum()<<endl;}

递归int Sum(int n,int tool=0){   if(n==1)   return n;  return (tool+=Sum(n-1,tool));}