fwt模板

int Pow(int x,int y){
    int ans=1;
    for (;y;y>>=1,x=1LL*x*x%mod)
        if (y&1)
            ans=1LL*ans*x%mod;
    return ans;
}
void FWT(int a[],int n,int flag){
    for (int d=1;d<n;d<<=1)
        for (int i=0;i<n;i+=(d<<1))
            for (int j=0;j<d;j++){
                int x=a[i+j],y=a[i+j+d];
                a[i+j]=(x+y)%mod;
                a[i+j+d]=(x-y)%mod;
                if (flag==-1){
                    a[i+j]=1LL*a[i+j]*inv2%mod;
                    a[i+j+d]=1LL*a[i+j+d]*inv2%mod;
                }
            }
}
bool check(int x,int n){
    for (int i=0;i<n;i++)
        b[i]=Pow(a[i],x);
    FWT(b,n,-1);
    b[v]=(b[v]+mod)%mod;
    return b[v]>0;
}