#include<iostream>
using namespace std;
int main()
{
int fibon[50];
int n;
while(cin>>n)
{
fibon[0]=0;
fibon[1]=1;
for(int i=2;i<=n;i++)
{
fibon[i]=fibon[i-1]+fibon[i-2];
}

cout<<fibon[n]<<endl;
}
return 0;
}