#include <bits/stdc++.h>

using namespace std;
typedef long long LL;
const int N = 110;
LL a[N];

int main() {
    int n;
    scanf("%d", &n);
    a[1] = a[2] = 1;
    for (int i = 3; i <= n; i++) a[i] = a[i - 1] + a[i - 2];
    printf("%lld.00", a[n]);
    return 0;
}