求解答,我该怎么样才能当输入小于2的数时输出错误呢,Fibonacci函数求详解啊
#include <iostream>using namespace std;unsigned fun(unsigned n){ if(n==1||n==2) return 1; else return fun(n-1)+fun(n-2);}int main(){ unsigned n; cout<<"输入n的值(n>2):"; if(n<=2) cout<<"输入有误"<<endl; cin>>n; unsigned y=fun(n); cout<<y<<endl; return 0;}