#include 
#include 
#include 
#include 
using namespace std;
const int maxn = 100;

int dp[maxn];
int fib(int n) {
    if(n == 1 or n == 2) {
        return 1;
    }
    if(dp[n] != -1) {
        return dp[n];
    }
    
    
    return dp[n] = fib(n - 1) + fib(n - 2);
}
int main() {
    for(int i = 0; i < maxn; i++) {
        dp[i] = -1;
    }
    
    int n;
    cin >> n;
    cout << fib(n) << endl;
    
    return 0;
}
// fib(4) = fib(3) + fib(2) = 2 + 1 = 3
// fib(3) = fib(2) + fib(1) = 1 + 1 = 2
// fib(2) = 1
// fib(1) = 1
// fib(2) = 1