#include "bits/stdc++.h"
using namespace std;
#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif
const int maxn = 5e5 + 5;
const int LG = 20;
int n, q;
string s;
int pfx[maxn], res[maxn];
vector<pair<int, int>> que[maxn];
pair<int, int> tree[maxn << 2];
pair<int, int> operator + (const pair<int, int> &a, const pair<int, int> &b) {
if (b.first == 1e9) return a;
if (a.first == 1e9) return b;
return make_pair(min(a.first, a.second + b.first), a.second + b.second);
}
void update(int pos, int val, int ind = 1, int l = 1, int r = n) {
if (l == r) {
tree[ind] = make_pair(val, val);
return;
}
int mid = (l + r) >> 1;
if (pos <= mid) update(pos, val, ind << 1, l, mid);
else update(pos, val, ind << 1 | 1, mid + 1, r);
tree[ind] = tree[ind << 1] + tree[ind << 1 | 1];
}
pair<int, int> get(int x, int y, int ind = 1, int l = 1, int r = n) {
if (l > y || r < x) return make_pair(1e9, 1e9);
if (x <= l and r <= y) {
return tree[ind];
}
int mid = (l + r) >> 1;
return get(x, y, ind << 1, l, mid) + get(x, y, ind << 1 | 1, mid + 1, r);
}
void solve() {
cin >> n >> s >> q;
s = ' ' + s;
for (int i = 1; i <= q; ++i) {
int l, r; cin >> l >> r;
que[r].emplace_back(l, i);
}
vector<int> vec;
for (int i = 1; i <= n; ++i) {
if (s[i] == 'T') {
vec.push_back(i);
} else {
update(i, 1);
if (!vec.empty()) {
update(vec.back(), -1);
vec.pop_back();
}
}
for (auto [v, id] : que[i]) {
int p = vec.end() - lower_bound(vec.begin(), vec.end(), v);
res[id] = p - min(0, get(v, i).first);
}
}
for (int i = 1; i <= q; ++i) {
cout << res[i] << '\n';
}
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
