#include <iostream>
using namespace std;
int main() {
int n;
cin>>n;
int a=1,b=1,c;
for(int i=2;i<=n;i++){
c=a+b;
a=b;
b=c;
}
if(n==0 || n==1)
cout<<1;
else
cout<<b;
return 0;
}
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