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(C++)

/**
 *    author:  cody
**/
#include <bits/stdc++.h>

using namespace std;

                    
typedef long long ll;
                
ll f[10000005], n;
int main()
{

 //freopen("tgcan.inp" , "r" , stdin);
 //freopen("tgcan.out" , "w" , stdout);

 ios::sync_with_stdio(false);
 cin.tie(0);
 
 f[1] = f[2] = 1;
 for (ll i = 3; i <= 10000000; ++i)
 {
  f[i] = f[i - 1] + f[i - 2];
 }             
 cin >> n;
 cout << f[n];
 return 0;
}