#include <iostream>
using namespace std;
int memo[400];
int f(int x)
{
if(memo[x]) return memo[x];
else if(x==0) return memo[x]=0;
else if(x==1) return memo[x]=1;
else return memo[x]=f(x-1)+f(x-2);
}
int main()
{
int n;
scanf("%d",&n);
printf("%d",f(n));
}