#include <iostream>
#include <cmath>
using namespace std;
int main()
{
int sum = 0;
int result = 0;
int n;
int f1=1, f2=1, f3=2;
bool p = true;
cin >> n;
for (int i = 1; i < n; ) {
f1 = f2;
f2 = f3;
f3 += f1;
p = true;
for (int r = 2; r < sqrt(f3); r++) {
if (f3%r == 0) p = false;
}
if (p) i++;
}
cout << f3;
return 0;
}
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