为啥这个程序会WA而不是RE啊？

#include<bits/stdc++.h>
#include<cstdio>
#define LL long long
using namespace std;
inline LL read(){
	LL x = 0, f = 1;char ch = getchar();
	while (ch < '0' || ch > '9') {if (ch == '-')f = -1;ch = getchar();}
	while (ch >= '0' && ch <= '9')x = x * 10 + (ch - '0'), ch = getchar();
	return x * f;
}
LL n,a[10001];
double a_,b_,Min=1000000;
inline double qwe(double now){
	return now*now;
}
bool fc(){
	a_=0,b_=0;
	for(LL i=1;i<=n;i++)a_+=a[i];
	a_/=n;
	for(LL i=1;i<=n;i++)b_+=qwe(double(a[i]*1.0-a_));
	if(b_*(n*1.0)<Min){Min=b_*(n*1.0);return 1;}
	return 0;
}
void dfs(){
	for(LL i=2;i<n;i++)
		if(a[i+1]+a[i-1]-a[i]!=a[i]){
			LL linshi=a[i];
			a[i]=a[i+1]+a[i-1]-a[i];
			if(fc())dfs();
			a[i]=linshi;
		}
	return ;
}
int main(){
	n=read();
	for(LL i=1;i<=n;i++)a[i]=read();
	fc();
	
	dfs();
	cout<<Min;
	return 0;
}