20分 QAQ 求大佬指点

#include <bits/stdc++.h>
using namespace std;
int main()
{
	double s,a=2,s1=2;
	int n=1;
	cin>>s;
	while(s1<s){
		n++;
		s1=s1+a*0.98;
}
	
	cout<<n<<endl;
	return 0;
}