[ AGC007 C ] Pushing Balls

题目

Atcoder

思路

发现这样的笔太骚, 不适合写题解, 以后不会用了

代码

#include <iostream>
using namespace std;
int n, x, d;
signed main() {
    cin >> n >> d >> x;
    double ad = d, ax = x, bd, bx, res = 0;
    while (n) {
        res += ad + n * ax - ax / 2;
        bd = ((2.0 * ad + 5.0 * ax) / (2.0 * n)) + ad;
        bx = ax + (4.0 * ax) / (2.0 * n);
        ax = bx, ad = bd, n--;
    }
    printf("%.10f\n", res);
    return 0;
}