#include using namespace std; #define rep(i,n) for(int (i) = 0 ; (i) < (int)(n) ; (i)++) #define REP(i,a,b) for(int (i) = a ; (int)(i) <= (int)(b) ; (i)++) #define all(n) (n).begin(),(n).end() typedef long long ll; typedef vector Vi; typedef vector VVi; typedef pair Pii; typedef vector VPii; int main(){ ll N; cin >> N; ll fib[51]; fib[0] = fib[1] = 1; for(int i = 2 ; i <= N ; i++) fib[i] = fib[i-1] + fib[i-2]; cout << fib[N] << endl; }