P8956 「CGOI-3」招魂术

代码（50pts也可以认为是10pts）希望大佬帮忙改正，蟹蟹：

#include<bits/stdc++.h>
using namespace std;
const int MOD=998244353;
int t,n;
long long A,B,X,Y;
long long ans;
long long POW(long long x,int y)
{
    long long aaa=1;
    while(y)
    {
        if(y&1) aaa=(aaa*x%MOD+MOD)%MOD;
        x=(x*x%MOD+MOD)%MOD; 
        y>>=1;
    }
    return aaa;
} 
int main()
{
    cin>>t;
    while(t--)
    {
        ans=1;
        scanf("%d%lld%lld%lld%lld",&n,&A,&B,&X,&Y);
        long long f1,f2;
        for(int i=1;i<=n;i++)
        {
            bool fg=0;
            if(i==1)
                f1=A,f2=X;
            else if(i==2) 
            {
                f1=B,f2=Y;
                B=A,Y=X;
            }
            else
            {
                A=floor(sqrtl((long double)(f1*B)))+1,X=floor(sqrtl((long double)(f2*Y)))+1;
                B=f1,Y=f2;
                f1=A,f2=X;
                if((f1==B&&f2==Y)||(f1==B+1&&f2==Y+1)||(f1==B&&f2==Y+1)||(f1==B+1&&f2==Y)) fg=1;
            }
            if(n<=100) fg=0;
            if(fg)
            {
                int z=n-i+1,x=f2-f1,y=Y-B;
                if((f1==B&&f2==Y)||(f1==B+1&&f2==Y+1))
                {
//                  cout<<"*"<<" ";
                    ans=(ans*POW(x,z)%MOD+MOD)%MOD;
                }
                else
                {
//                  cout<<"/"<<" ";
                    if(z%2==1)
                    {
                        ans=(ans*x%MOD+MOD)%MOD;
                    }
                    z/=2;
                    ans=(ans*POW(x*y,z)%MOD+MOD)%MOD;
                }
//              cout<<f1<<" "<<f2<<endl;
                break;
            }
            ans=((ans*(f2-f1))%MOD+MOD)%MOD;
//          cout<<f1<<" "<<f2<<endl;
        }
        ans=(ans+MOD)%MOD;
        printf("%lld\n",ans);
    }
    return 0;
}