#include 

using namespace std;

int memo[1005];
int fib(int x) {
    if(x == 1) {
        return 1;
    }
    if(x == 2) {
        return 1;
    }
    if(memo[x] != -1) {
        return memo[x];
    }
    memo[x] = fib(x - 1) + fib(x - 2);
    return memo[x];
}
int main()
{
    int n;
    cin >> n;
    for(int i = 1; i <= n; i++) {
        memo[i] = -1;
        // -1 znaci deka ne e presmetano
        // se sto e razlicno od -1 znaci deka ni e presmetano
        
    }
    cout << fib(n) << endl;
    return 0;
}
// fib(7) --> fib(6) + fib(5) = 8 + 5 = 13 memo[7] = 13
// fib(6) --> fib(5) + fib(4) = 5 + 3 = 8 memo[6] = 8
// fib(5) --> fib(4) + fib(3) = 3 + 2 = 5 memo[5] = 5
// fib(4) --> fib(3) + fib(2) = 2 + 1 = 3 memo[4] = 3
// fib(3) --> fib(2) + fib(1) = 1 + 1 = 2  memo[3] = 2
// fib(2) --> 1 memo[2] = 1
// fib(1) --> 1 memo[1] = 1;