C++ 代码
#include<bits/stdc++.h>
#include<cstdio>
using namespace std;
int main(){
int a, n = 0, sum = 0;
scanf("%d",&a);
while (n <= 0) {
scanf("%d",&n);
}
for (int i = a; i < a+n; i++) sum += i;
printf("%d", sum);
return 0;
}