import java.math.BigInteger;

public class prob25 {
  public static void main(String args[]) {
    BigInteger n1 = new BigInteger("1");
    BigInteger n2 = new BigInteger("1");
    BigInteger old;
    String s;
    int n = 2;
    do {
      old = n2;
      n2 = n2.add(n1);
      n1 = old;
      s = n2.toString();
      n++;
    } while (s.length() < 1000);
    System.out.println("" + n);
  }
}