text: // UVa10334 Ray Through Glasses
  // Rujia Liu
  #include<cstdio>
  #include<cstring>
  #include<iostream>
  #include<vector>
  using namespace std;
  
  struct BigInteger {
    static const int MOD = 1000000000;
    vector<int> s;
  
    BigInteger(int num=0) { *this = num; }
    BigInteger operator = (int num) { s.clear(); s.push_back(num); return *this; }
  
    BigInteger operator + (const BigInteger& b) const {
      BigInteger c;
      c.s.clear();
      for(int i = 0, g = 0; ; i++) {
        if(g == 0 && i >= s.size() && i >= b.s.size()) break;
        int x = g;
        if(i < s.size()) x += s[i];
        if(i < b.s.size()) x += b.s[i];
        c.s.push_back(x % MOD);
        g = x / MOD;
      }
      return c;
    }
  
    BigInteger operator += (const BigInteger& b) { *this = *this + b; return *this; }
  };
  
  ostream& operator << (ostream &out, const BigInteger& x) {
    cout << x.s.back();
    for(int i = x.s.size()-2; i >= 0; i--) {
      char buf[20];
      sprintf(buf, "%09d", x.s[i]);
      for(int j = 0; j < strlen(buf); j++) cout << buf[j];
    }
    return out;
  }
  
  const int maxn = 1000;
  
  BigInteger f[maxn+1];
  
  int main() {
    f[0] = 1;
    f[1] = 2;
    for(int i = 2; i <= maxn; i++)
      f[i] = f[i-2] + f[i-1];
    int n;
    while(cin >> n) cout << f[n] << "\n";
    return 0;
  }
  