有点废话的题解

#include<bits/stdc++.h>
using namespace std;
typedef long long apple;
apple pear(apple n,apple sum=0){
    for(int i=1;i<=n;i++) sum=sum+i;
    return sum;
}
int main(){
    apple n;
    cin>>n;
    cout<<pear(n);
    return 0;
}