题解

#include<bits/stdc++.h>
using namespace std;
double a,num=2,n,n1;
int x;
int main(){
    cin>>a;
    while(num<a){
        x++;
        num+=n*0.98;
        n=num-n1;
        n1=num;
    }
    cout<<x;
    return 0;
}