// 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];
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;
}
int main() {
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i];
cin >> q;
for (int i = 1; i <= q; i++) {
int l, r; cin >> l >> r;
qu[r].push_back({l, i});
}
int cur = 0, mn = 0;
for (int i = 1; i <= n; i++) {
if (a[i] == 'T') {
s.push(i);
upd(1, i, 1);
}
else {
if (mn && !s.empty()) {
mn--;
cur--;
upd(1, s.top(), -1);
s.pop();
}
cur++;
}
mn = min(mn + cur, cur);
for (auto [a, b] : qu[i]) {
ans[b] = qry(a);
}
}
for (int i = 1; i <= q; i++) cout << ans[i] << '\n';
}
