#include <iostream>
#include<cmath>
using namespace std;
int main() {
long long int a[50000];
a[0]=1;
a[1]=1;
for(long long i=2;i<50000;++i)
a[i]=a[i-1]+a[i-2];
long long k;
cin>>k;
cout<<a[k];
return 0;
}
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