import java.util.*;
import java.math.*;
import static java.math.BigInteger.*;

class Main {
    public static BigInteger fib(int l) {
	BigInteger x = ZERO;
	BigInteger y = ONE;
	for (int i = 0; i < l; ++i) {
	    BigInteger z = x.add(y);
	    x = y;
	    y = z;
	}
	return x;
    }
    public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	int l = sc.nextInt();
	if (l == 2) {
	    System.out.println("3\nINF");
	    return;
	}
	if (l % 2 == 1) {
	    System.out.println(fib(l));
	} else {
	    BigInteger tmp = fib(l / 2);
	    System.out.println(fib(l).subtract(tmp.multiply(tmp)));
	}
    }
}