// https://oj.uz/problem/view/CEOI17_oneway
#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e5+10;
int n, m, P;
vector<pair<int, int>> g[maxn];
bool f[maxn];
int d[maxn];
int dp[maxn];
int pai[maxn];
char ans[maxn];
pair<int, int> io[maxn];
int T;
set<pair<int, int>> in;
set<pair<int, int>> already;
map<pair<int, int>, int> ruas;
pair<int, int> sp[maxn];
pair<int, int> tr[4*maxn]; // max min
bool root[maxn];
pair<int, int> merge(pair<int, int> a, pair<int, int> b)
{
return {max(a.first, b.first), min(a.second, b.second)};
}
void build(int no, int l, int r)
{
if(l == r) tr[no] = {-maxn, maxn};
else
{
int lc = 2*no; int rc = 2*no+1; int mid = (l+r)/2;
build(lc, l, mid);
build(rc, mid+1, r);
tr[no] = merge(tr[lc], tr[rc]);
}
}
void update(int no, int l, int r, int pos, int val)
{
if(l == r) tr[no] = merge(tr[no], {val, val});
else
{
int lc = 2*no; int rc = 2*no+1; int mid = (l+r)/2;
if(pos <= mid) update(lc, l, mid, pos, val);
else update(rc, mid+1, r, pos, val);
tr[no] = merge(tr[lc], tr[rc]);
}
}
pair<int, int> query(int no, int l, int r, int L, int R)
{
if(r < L || R < l) return {-maxn, maxn};
else if(L <= l && r <= R) return tr[no];
else
{
int lc = 2*no; int rc = 2*no+1; int mid = (l+r)/2;
return merge(query(lc, l, mid, L, R), query(rc, mid+1, r, L, R));
}
}
void dfs(int x, int ant)
{
io[x].first = ++T;
f[x] = 1;
for(auto[i, t] : g[x])
{
if(i == ant) continue;
if(f[i])
{
ans[t] = 'B';
if(d[i] > d[x]) dp[x]--;
else dp[x]++;
continue;
}
d[i] = d[x]+1;
pai[i] = x;
dfs(i, x);
dp[x] += dp[i];
}
io[x].second = T;
}
int main()
{
cin >> n >> m;
for(int i = 1; i <= m; i++)
{
int a, b;
cin >> a >> b;
if(a == b) ans[i] = 'B';
else if(in.count({a, b}) || in.count({b, a}))
{
ans[i] = 'B';
already.insert({a, b});
already.insert({b, a});
}
else
{
in.insert({a, b});
ruas[{a, b}] = i;
ruas[{b, a}] = i;
}
}
for(auto[a, b] : in)
{
int i = ruas[{a, b}];
if(already.count({a, b})) ans[i] = 'B';
g[a].push_back({b, i});
g[b].push_back({a, i});
}
for(int i = 1; i <= n; i++)
{
if(f[i]) continue;
dfs(i, 0);
root[i] = 1;
}
cin >> P;
for(int i = 0; i < P; i++)
{
int a, b;
cin >> a >> b;
sp[i] = {a, b};
}
build(1, 1, T);
for(int i = 0; i < P; i++)
{
auto[a, b] = sp[i];
update(1, 1, T, io[a].first, io[b].first);
}
for(int i = 1; i <= n; i++)
{
if(root[i]) continue;
int p = pai[i];
int j = ruas[{p, i}];
if(ans[j] == 'B' || ans[j] == 'L' || ans[j] == 'R') continue;
if(dp[i] != 0)
{
ans[j] = 'B';
continue;
}
pair<int, int> x = query(1, 1, T, io[i].first, io[i].second);
if(x.first > io[i].second || x.second < io[i].first)
{
ans[j] = 'R';
}
}
build(1, 1, T);
for(int i = 0; i < P; i++)
{
auto[a, b] = sp[i];
update(1, 1, T, io[b].first, io[a].first);
}
for(int i = 2; i <= n; i++)
{
int p = pai[i];
int j = ruas[{p, i}];
if(ans[j] == 'B' || ans[j] == 'L' || ans[j] == 'R') continue;
if(dp[i] != 0)
{
ans[j] = 'B';
continue;
}
pair<int, int> x = query(1, 1, T, io[i].first, io[i].second);
if(x.first > io[i].second || x.second < io[i].first)
{
ans[j] = 'L';
}
else ans[j] = 'B';
}
string gans;
for(int i = 1; i <= m; i++)
{
gans += ans[i];
}
cout << gans;
return 0;
}
