#include<iostream>
#include<vector>
using namespace std;
int main(){
    int n;
    cin >> n;
    vector<int>arr(n);
    arr[0]=1;
    arr[1]=1;
    for(int k=2;k<n;k++){
        arr[k]=arr[k-1]+arr[k-2];
    }
    cout << arr[n-1] <<endl;
    return 0;
}