P1423 小玉在游泳

题目传送门

#include <bits/stdc++.h>

using namespace std;
double k;
double x;

int main() {
    cin >> k;
    for (int cnt = 1;; cnt++) {
        x += 2.0 * pow(0.98, cnt - 1);
        if (x >= k) {
            cout << cnt << endl;
            exit(0);
        }
    }
}