#include <iostream>
using namespace std;
int fact(int a)
{
int k = 0;
if(a == 1 || a == 2) return 1;
else
{
for(int i = 1; i <= a; i++)
{
int x[30];
x[1] = 1;
x[2] = 1;
x[i] = x[i-1] + x[i-2];
k = x[i];
}
return k;
}
}
int main()
{
int a;
cin >> a;
int t = fact(a);
cout << t;
return 0;
}