#include<bits/stdc++.h>
using namespace std;
string add(string s1,string s2)
{
    int i,j,k,sum=0,carry=0,len1,len2;
    string ans="";
    if(s1.length()>s2.length())
        swap(s1,s2);
    reverse(s1.begin(),s1.end());
    reverse(s2.begin(),s2.end());
    len1=s1.length();
    len2=s2.length();
    for(i=0;i<len1;i++)
    {
        sum=(s1[i]-'0' + s2[i]-'0')+carry;
        ans.push_back(sum%10 + '0');
        carry=sum/10;
    }
    for(i=len1;i<len2;i++)
    {
        sum=(s2[i]-'0')+carry;
        ans.push_back(sum%10 + '0');
        carry=sum/10;
    }
    if(carry)
    {
        ans.push_back(carry + '0');
    }
    reverse(ans.begin(),ans.end());
    return ans;
}
int main()
{
    string s[6000];
    int i,j,k,n;
    s[1]='1';
    s[2]='1';
    for(i=3;i<=5005;i++)
    {
        s[i]=add(s[i-1],s[i-2]);
     //   cout<<s[i]<<endl;
    }
    while(scanf("%d",&n)==1)
    {
        cout<<s[n]<<endl;
    }
    return 0;
}