我这里求的是斐波那契数列，第0,1项分别是0,1，怎么从第二项往后输出结果都是0呢？

#include<bits/stdc++.h>
using namespace std;
const int maxn=40;
int state[maxn]={0,1};
int n,sum;
void Fibonacci(int u){
    if(u==n-1){
        printf("%d\n",sum);
        return;
    }if(u==0 || u==1){
        if(u==0) printf("0\n");
        if(u==1) printf("1\n");
    }else{
        state[u]=state[u-1]+state[u-2];
        sum+=state[u];
        Fibonacci(u+1);
    }
}
int main(){
    scanf("%d",&n);
    Fibonacci(0);
    return 0;