#include <iostream>

unsigned int fib(unsigned int &n);

unsigned int fib(unsigned int &n) {

    unsigned int t = 0;
    unsigned int r = 0;

    for (unsigned int i = 0; i <= n; i++) {
        if (i != 0 && i < 3) {
            t = 1;
            r = 0;
        } else if (i > 4) {
            t = r - t;
        }

        r = t + r;
    }

    return r;

}

int main() {
    unsigned int n;
    std::cout << "Bitte geben sie einen Wert ein:\n";
    std::cout << "n = ";
    std::cin >> n;
    std::cout << "Fib(" << n << ")=" << fib(n) << std::endl;
    return 0;
}