#include <stdio.h>
#include <stdlib.h>

unsigned long int
fib(unsigned long int n)
{
	if (n <= 1) return n;
	return fib(n - 1) + fib(n - 2);
}

int
main(int argc, char **argv)
{
	unsigned long n = 0;
	scanf("%lu", &n);
	//size_t rd = read(0, recv_buf, 1000*1024);
        //if (rd <= 0) return -1;

        //      unsigned long long st = get_time(), en;
        //r = fib(30);
        //      en = get_time();
	for (int i = 0; i < 3; i++)
	{
		n = fib(n);
	}
	
    printf("%lu\n", n);

	return 0;
}