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