#include <stdio.h>
#include <stdlib.h>
int main()
{
int n;
double first, needs, target, M;
scanf("%lf", &target);
first = 2.0;
n = 1;
needs = first;
M = first;
while (1) //死循環
{
if (needs > target) //判斷是否符合條件
{
printf("%d\n", n);
break;
}
M = M * 0.98; //每一步為上一步的98%,M(=2.0)的累積
needs += M; //總共游的距離needs(=2.0)的累加
n++;
}
return 0;
}