#include<iostream>
  using namespace std;
   int main ()
      {
         int n;
         cin>>n;
        int a,b;
           a=1;
           b=1;
    
         int i=0;
       while (i<n-1)
             {
         int c=a+b;
             a=b;
             b=c;
             i++;
            }
       cout <<a <<endl;
       return 0;
  }