#include <iostream>
#include <vector>
using namespace std;
int memo[105];
int fib(int n) {
    if(n <= 2) {
        return 1;
    }
    if(memo[n] != -1) {
        return memo[n];
    }
    return memo[n] = fib(n - 1) + fib(n - 2);
}
int main() {
    int n;
    cin >> n;
    for(int i = 0; i <= n; i++) {
        memo[i] = -1;
    }
    cout << fib(n) << endl;
    return 0;
}
// fib(7) = fib(6) + fib(5)
//