今日学习在线编程题：等差数列

题目来源：码蹄集

https://matiji.net/exam/brushquestion/222/778/B3FCFEC101BD05189BB74D522E019504

 

参考程序：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cmath>
using namespace std;
#define N 1000
#define ll long long 
int main(){
    int n, m, k;
    cin >> n >> m >> k;
    ll ans = 0;
    for (int i = m, j = 1; j <= n; j++, i = i + k ){
        ans += i ;
    }
    cout << ans;
    return 0;
}