#include <iostream>
using namespace std;
int main()
{
double a;
int day = 0;
cin>>a;
while(a > 70){
day++;
a = a*98/100;
}
cout<<day;
#include <iostream>
using namespace std;
int main()
{
double a;
int day = 0;
cin>>a;
while(a > 70){
day++;
a = a*98/100;
}
cout<<day;
}