#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pi pair<int, int>
#define vi vector<int>
#define vs vector<string>
#define vb vector<bool>
#define vpi vector<pi>
#define pb push_back
#define all(a) (a).begin(), (a).end()
const int mod = 1e9 + 7;
void solve()
{
int n;
cin >> n;
vector<vi> grid(100, vi(100, -1));
for (int i = 0; i < n; i++)
{
int h;
cin >> h;
for (int j = 0; j < h; j++)
{
grid[j][i] = 0;
}
}
for (int i = 0; i < n; i++)
{
int w;
cin >> w;
}
grid[0][n - 1] = 1;
for (int i = n - 2; i >= 0; i--)
{
grid[0][i] = grid[0][i + 1] + 1;
}
for (int l = 1; l < 100; l++)
{
for (int i = n - 1; i >= 0; i--)
{
if (grid[l][i] == -1)
continue;
if (grid[l][i + 1] == -1)
{
grid[l][i] = l + 1;
}
else
{
grid[l][i] = ((grid[l - 1][i] + grid[l][i + 1]) - grid[l - 1][i + 1]) + 1;
}
grid[l][i] %= mod;
}
}
int ans = 0;
for (int i = 0; i < 100; i++)
{
for (int j = 0; j < 100; j++)
{
ans = (ans + (grid[i][j] == -1 ? 0 : grid[i][j])) % mod;
}
}
cout << ans << '\n';
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
int t = 1;
// cin >> t;
while (t--)
{
solve();
}
return 0;
}
