#include <bits/stdc++.h> using namespace std;

int main() { int n; cin >> n; if (n == 1 || n == 2) { cout << 1 << endl; return 0; } int a = 1; int b = 1; int c;

for (int i = 3; i <= n; i++) {
	c = a + b;
	a = b;
	b = c;
}
cout << b << endl;
return 0;

}