#include<iostream>
using namespace std;
int main()
{
long long int n, a[51] = { 0,1, 2 };
while (cin >> n)
{
for (int i = 3; i <51; i++)
{
a[i] = a[i - 1] + a[i - 2];
}
cout << a[n] << endl;
}
return 0;
}
using namespace std;
int main()
{
long long int n, a[51] = { 0,1, 2 };
while (cin >> n)
{
for (int i = 3; i <51; i++)
{
a[i] = a[i - 1] + a[i - 2];
}
cout << a[n] << endl;
}
return 0;
}