#include <iostream>
#include <math.h>
using namespace std;
int main() {
int N;
int tr[10001];
cin >> N;
tr[0] = 1;
tr[1] = 1;
for (int i = 2; i <= N; i++)
{
tr[i] = tr[i - 1] + tr[i - 2];
}
cout << tr[N-1] << endl;
return 0;
}
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