/**
* code generated by JHelper
* More info: https://github.com/AlexeyDmitriev/JHelper
* @author
*/
#include <bits/stdc++.h>
using namespace std;
#define long long long
const long MOD = 1e9+7, LINF = 1e18 + 1e16;
const int INF = 1e9+1;
const double EPS = 1e-10;
const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
const int N = 1 << 19;
class Elections {
int n, q, ans[N];
string s;
vector<pair<int,int> > qq[N];
int mn[2*N], lz[2*N];
void apply(int i, int l, int r) {
if(!lz[i]) return;
mn[i] += lz[i];
if(i < N) {
lz[i << 1] += lz[i];
lz[i << 1 | 1] += lz[i];
}
lz[i] = 0;
}
void update_mn(int tl, int tr, int v, int i = 1, int l = 0, int r = N-1) {
apply(i, l, r);
if(r < tl || l > tr) return;
if(tl <= l && r <= tr) {
lz[i] += v;
apply(i, l, r);
return;
}
int mid = l+r >> 1;
update_mn(tl, tr, v, i << 1, l, mid);
update_mn(tl, tr, v, i << 1 | 1, mid+1, r);
mn[i] = min(mn[i << 1], mn[i << 1 | 1]);
}
int query_mn(int tl, int tr, int i = 1, int l = 0, int r = N-1) {
apply(i, l, r);
if(r < tl || l > tr) return INF;
if(tl <= l && r <= tr) return mn[i];
int mid = l+r >> 1;
return min(query_mn(tl, tr, i << 1, l, mid), query_mn(tl, tr, i << 1 | 1, mid+1, r));
}
public:
void run(istream &cin, ostream &cout) {
cin >> n >> s >> q;
for(int i = 0, l, r; i < q; i++) {
cin >> l >> r;
--l, --r;
qq[r].emplace_back(l, i);
}
vector<int> ts;
for(int i = 0; i < n; i++) {
if(s[i] == 'T') ts.push_back(i);
else {
if(!ts.empty()) {
update_mn(ts.back(), n-1, -1);
ts.pop_back();
}
update_mn(i, n-1, 1);
}
for(auto p: qq[i]) {
int j, qidx;
tie(j, qidx) = p;
int res = query_mn(j, i) - (j > 0 ? query_mn(j-1, j-1) : 0);
auto it = lower_bound(ts.begin(), ts.end(), j);
int cnt = (int) ts.size() - (it - ts.begin());
// cout << qidx << ' ' << cnt << ' ' << res << endl;
ans[qidx] = cnt - min(res, 0);
}
}
for(int i = 0; i < q; i++) cout << ans[i] << '\n';
}
};
class Solver {
public:
void solve(std::istream& in, std::ostream& out) {
Elections *obj = new Elections();
obj->run(in, out);
}
};
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
Solver solver;
std::istream& in(std::cin);
std::ostream& out(std::cout);
solver.solve(in, out);
return 0;
}
