#include <iostream>
using namespace std;
int main()
{
		
	double n = 2, a = 2, x;
	cin >> x;
	int cnt = 1;
	while (a < x)
	{
		n *= 0.98;
		a += n;
		cnt++;
	}
	cout << cnt << endl;
	return 0;
} //代码已AC

先赞后搬

#include<bits/stdc++.h>
using namespace std;
double x,num;
int main()
{
    double l=2;
    cin>>x;
    while(x>0)
    {
        num++;
        x-=l;
        l*=0.98;
    }
    cout<<num;
    return 0;
}

已AC