#include <cstdio>
unsigned char f1[212] = {1, 1}, f2[212] = {1, 2};
void adun(unsigned char f1[], unsigned char f2[])
{
    int t = 0;
    for(int i = 1; i <= f2[0] ; i++)
    {
        t += f1[i] + f2[i];
        f1[i] = t % 10;
        t /= 10;
    }
    f1[0] = f2[0];
    while(t > 0)
    {
        f1[++f1[0]] = t % 10;
        t /= 10;
    }
}
void afisare(unsigned char a[])
{
    freopen("nunta.out", "w",stdout);
    for(int i = a[0]; i > 0; i--)
        fputc(a[i]+'0', stdout);
    fclose(stdout);
}
void fib(int N)
{
    unsigned char *p1 = &f1[0], *p2 = &f2[0], *px;
    if(N == 1)p2 = p1;
    for(int i = 3; i <= N; i++)
    {
        adun(p1, p2);
        px = p1;
        p1 = p2;
        p2 = px;
    }
    afisare(p2);
}


int main()
{
    int N;
    freopen("nunta.in", "r",stdin);
    scanf("%d", &N);
    fclose(stdin);
    fib(N);
    return 0;
}