include<iostream>

using namespace std;

int Fibonacci(int n)
{
if(n==0) return 0;
if(n==1) return 1;
if(n==2) return 1;
else return Fibonacci(n-1)+Fibonacci(n-2);
}

int main()
{
int n;
cin>>n;
cout<<Fibonacci(n)<<endl;
}