#include <bits/stdc++.h>
using namespace std;
#define int long long
#ifndef yoshi_likes_e4
#define endl '\n'
#endif
#define problem "election"
#define multitest 0
#define debug(x) cerr << #x << " = " << x << endl;
void init()
{
}
struct Node
{
int RS;
int Sum = 0;
Node()
{
RS = 1e9;
}
Node(int x)
{
RS = Sum = x;
}
};
Node merge(const Node &L, const Node &R)
{
if (L.RS == 1e9)
return R;
if (R.RS == 1e9)
return L;
Node res;
res.RS = min(R.RS, R.Sum + L.RS);
res.Sum = L.Sum + R.Sum;
return res;
}
struct ST
{
vector<Node> t;
int n = 0;
ST()
{
}
ST(int n) : n(n)
{
t.resize(2 * n);
fill(t.begin() + n, t.end(), Node(0));
for (int i = n - 1; i > 0; i--)
t[i] = merge(t[2 * i], t[2 * i + 1]);
}
void modify(int p, int value)
{
for (t[p += n] = value; p > 1; p >>= 1)
t[p >> 1] = merge(t[p - (p & 1)], t[p + (~p & 1)]);
}
Node query(int l, int r)
{
Node resl, resr;
for (l += n, r += n; l < r; l >>= 1, r >>= 1)
{
if (l & 1)
resl = merge(resl, t[l++]);
if (r & 1)
resr = merge(t[--r], resr);
}
return merge(resl, resr);
}
};
ST Stx(500000);
struct Tp3
{
int x, y, z;
};
void Yoshi()
{
int n;
cin >> n;
string s;
cin >> s;
int q;
cin >> q;
vector<Tp3> qus(q);
for (auto &i : qus)
cin >> i.x >> i.y, i.x--, i.y--, i.z = &i - &qus[0];
sort(qus.begin(), qus.end(), [](auto &a, auto &b) { return a.x > b.x; });
vector<int> Tp, qres(q);
int ptr = n - 1;
for (auto &[l, r, id] : qus)
{
while (ptr >= l)
{
if (s[ptr] == 'T')
Tp.push_back(ptr);
else
{
Stx.modify(ptr, 1);
if (Tp.size())
{
Stx.modify(Tp.back(), -1);
Tp.pop_back();
}
}
ptr--;
}
qres[id] = upper_bound(Tp.rbegin(), Tp.rend(), r) - Tp.rbegin() - Stx.query(l, r + 1).RS;
}
for (auto &i : qres)
cout << i << endl;
}
signed main()
{
#ifndef yoshi_likes_e4
ios::sync_with_stdio(0);
cin.tie(0);
if (fopen(problem ".inp", "r"))
{
freopen(problem ".inp", "r", stdin);
freopen(problem ".out", "w", stdout);
}
#endif
init();
int t = 1;
#if multitest
cin >> t;
#endif
while (t--)
Yoshi();
}
