斐波那契数列(按值传递)

#include <bits/stdc++.h>
using namespace std;

int NUM ( int a)
{
    if(a<2) return a;
    else return NUM(a-1) + NUM (a-2);
}
int main()
{
    int NUMx , NUMy;
    cin >> NUMx ;
    cout << NUM (NUMx);
    return 0;
}