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#include<bits/stdc++.h>
#define lim 500009
#define mk make_pair
#define ff first
#define sc second

using namespace std;

typedef unsigned int uint;

const int md = 1000000007;
int n;
int t[2][lim][3];

void akt(int ii,int i)
{
	if((t[ii][i][1]>0)&&(t[ii][t[ii][i][1]][0]!=i))
	{
		t[ii][i][1] = t[ii][t[ii][i][1]][0];
		akt(ii,i);
	}
	if((t[ii][i][2]>0)&&(t[ii][t[ii][i][2]][0]!=i))
	{
		t[ii][i][2] = t[ii][t[ii][i][2]][0];
		akt(ii,i);
	}
}

long long rem(int dir,int ii,int i)
{
	if(i == 0)
	{
		return 0;
	}
	long long wyn = abs(t[ii][i][0]-i)-1;
	//printf("%lld %d %d %d\n", wyn, dir, ii, i);
	if(dir)
	{
		wyn = (wyn+rem(dir,ii,t[ii][i][1]))%md;
		wyn = (wyn+rem(dir,ii,t[ii][i][2]))%md;
		t[ii][i][0] = (n+i)%(n+1);
		t[ii][i][1] = 0;
		t[ii][i][2] = (i+1)%(n+1);
	}
	else
	{
		wyn = (wyn+rem(dir,ii,t[ii][i][1]))%md;
		wyn = (wyn+rem(dir,ii,t[ii][i][2]))%md;
		t[ii][i][0] = (i+1)%(n+1);
		t[ii][i][1] = (n+i)%(n+1);
		t[ii][i][2] = 0;
	}
	return wyn;
}

long long rot(int dir,int ii,int i)
{
	long long wyn = 0;
	//printf("%d %d %d %d\n", dir, ii, i, t[ii][i][dir+1]);
	if(dir)
	{
		if((i==0)||(t[ii][i][2]==0))
		{
			exit(0);
		}
		wyn = rem(dir,0,t[ii][t[ii][i][2]][1])+abs(i-t[ii][i][2])-1;
		if(wyn>0)
		{
			t[ii][t[ii][i][2]][0] = t[ii][i][2]-1;
			t[ii][t[ii][i][2]][1] = 0;
			t[ii][i][2] = i+1;
		}
		int pom = t[ii][i][2];
		t[ii][pom][0] = t[ii][i][0];
		t[ii][i][0] = pom;
		t[ii][i][2] = 0;
		t[ii][pom][1] = i;
		akt(ii,t[ii][pom][0]);
	}
	else
	{
		if((i==0)||(t[ii][i][1]==0))
		{
			exit(0);
		}
		wyn = rem(dir,0,t[ii][t[ii][i][1]][2])+abs(i-t[ii][i][1])-1;
		if(wyn>0)
		{
			t[ii][t[ii][i][1]][0] = t[ii][i][1]+1;
			t[ii][t[ii][i][1]][2] = 0;
			t[ii][i][1] = i-1;
		}
		int pom = t[ii][i][1];
		t[ii][pom][0] = t[ii][i][0];
		t[ii][i][0] = pom;
		t[ii][i][1] = 0;
		t[ii][pom][2] = i;
		akt(ii,t[ii][pom][0]);
	}
	wyn = (wyn+1)%md;
	return wyn;
}

long long f(int i)
{
	//printf("##%d\n", i);
	long long wyn = 0;
	while(t[0][i][1]!=t[1][i][1])
	{
		if(t[0][i][1]<t[1][i][1])
		{
			wyn = (wyn+rot(1,0,t[0][i][1]))%md;
		}
		else
		{
			wyn = (wyn+rot(0,0,t[0][i][1]))%md;
		}
	}
	while(t[0][i][2]!=t[1][i][2])
	{
		//printf("%lld  %d %d\n", wyn, t[0][i][2], t[1][i][2]);
		if(t[0][i][2]<t[1][i][2])
		{
			wyn = (wyn+rot(1,0,t[0][i][2]))%md;
		}
		else
		{
			wyn = (wyn+rot(0,0,t[0][i][2]))%md;
		}
	}
	//printf("%lld\n", wyn);
	if(t[0][i][1]>0) wyn = (wyn+f(t[0][i][1]))%md;
	if(t[0][i][2]>0) wyn = (wyn+f(t[0][i][2]))%md;
	return wyn;
}

int main()
{
	scanf("%d", &n);
	for(int ii = 0;ii<2;++ii)
	{
		for(int i = 1;i<=n;++i)
		{
			int a;
			scanf("%d", &a);
			a = max(a,0);
			t[ii][i][0] = a;
			if(i<a)
			{
				t[ii][a][1] = i;
			}
			else
			{
				t[ii][a][2] = i;
			}
		}
	}
	
	
	printf("%lld\n", f(0));
}
/*
11
-1 9 5 3 6 2 6 7 1 9 10
2 3 6 5 3 -1 8 6 11 9 8

29
//*/