// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
using namespace std;
stack <int> s;
char a[500005];
vector <pair <int, int> > qu[500005];
int ft[500005], ans[500005], prv[500005], nxt[500005];
int n, q;
void upd (int l, int r, int v) {
for (; l <= n; l += (l & -l)) ft[l] += v;
r++;
for (;r <= n; r += (r & -r)) ft[r] -= v;
}
int qry (int p) {
int res = 0;
for (;p;p-=(p & -p)) res += ft[p];
return res;
}
struct node{
int s, e, m, sm, suf, pref;
node *l, *r;
node (int _s, int _e) {
s = _s, e = _e, m = (s + e) >> 1;
if (s != e)l = new node(s, m), r = new node(m + 1, e);
sm = suf = 0;
}
void upd (int p, int v) {
if (s == e) sm = suf = pref = v;
else {
if (p <= m) l->upd(p, v);
else r->upd(p, v);
sm = l->sm + r->sm;
suf = min(r->suf, r->sm + l->suf);
pref = min(l->pref, r->pref + l->sm);
}
}
pair <int, int> qry (int a, int b) {
if (a == s && b == e) return {suf, sm};
else if (b <= m) return l->qry(a, b);
else if (a > m) return r->qry(a, b);
else {
pair <int, int> tmp = r->qry(m + 1, b), tmp2 = l->qry(a, m);
return {min(tmp.second, tmp.first + tmp2.second), tmp.second + tmp2.second};
}
}
pair <int, int> qry2 (int a, int b) {
if (a == s && b == e) return {pref, sm};
else if (b <= m) return l->qry2(a, b);
else if (a > m) return r->qry2(a, b);
else {
pair <int, int> tmp = r->qry2(m + 1, b), tmp2 = l->qry2(a, m);
return {min(tmp2.first, tmp2.second + tmp.first), tmp.second + tmp2.second};
}
}
}*root;
int main() {
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i];
nxt[n + 1] = n + 1;
for (int i = n; i >= 1; i--) {
nxt[i] = nxt[i + 1];
if (a[i] == 'C') nxt[i] = i;
}
cin >> q;
for (int i = 1; i <= q; i++) {
int l, r; cin >> l >> r;
qu[r].push_back({l, i});
}
root = new node(1, n);
int cur = -1, mn = 0;
for (int i = 1; i <= n; i++) {
if (a[i] == 'T') {
s.push(i);
prv[i] = prv[i - 1];
upd(1, i, 1);
}
else {
if (!s.empty()) {
int lo = 1, hi = s.top()-1, v = lo - 1;
while (lo <= hi) {
int mid = (lo + hi) >> 1;
if (root->qry2(mid, i).first > 0) v = mid, lo = mid + 1;
else hi = mid - 1;
}
cur = s.top();
//cout << v << ' ' << root->qry(4, 9).first << '\n';
mn--;
upd(1, v, -1);
root->upd(s.top(), -1);
s.pop();
}
root->upd(i, 1);
prv[i] = i;
mn = min(mn + 1, 1);
}
for (auto [a, b] : qu[i]) {
ans[b] = qry(a);
}
}
for (int i = 1; i <= q; i++) cout << ans[i] << '\n';
}
