// Telebe of adicto yani AzeTurk810
// Why i am not a teacher? ?(idea from Ayxan007)
#include <bits/stdc++.h>
using namespace std;
using ll= int64_t;
using ull=unsigned int64_t;
# define mpll map<ll,ll>
# define umpll unordered_map<ll,ll>
# define vv vector<vector
# define vint vector<int>
# define vull vector<unsigned long long>
# define sint set<int>
# define vpri vector<pair<int,int>>
# define vll vector<long long>
# define vbl vector<bool>
# define vvint vector<vector<int>>
# define vvll vector<vector<long long>>
/* Other defines*/
# define qint queue<int>
//# define endl '\n'
# define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
# define range(a,b,c) for(int i=a;i<b;i+=c)
# define ranger(a,b,c) for(int r=a;r<b;r+=c)
# define arange(a,b,c) for(int i=a;i>b;i-=c)
# define bend(x) (x).begin(),(x).end()
# define pb push_back
# define sortv(v) sort((v).begin() , (v).end());
# define fori(x) for(int i=0;i<x;i++)
# define forj(y) for(int j=0;j<y;j++)
# define fori1(x) for(int i=1;i<=x;i++)
# define forj1(y) for(int j=1;j<=y;j++)
# define forn(x,c) for(int i=0;i<n;i+=c)
# define ff first
# define ss second
# define INFi 1e15
# define INFll 1e18
# define printfprs(v) for(int alma = 0;alma<(v).size();alma++){cout<<(v)[alma].ff<< ' '<<(v)[alma].ss<<endl;};
# define printfv(v) {for(int alol = 0 ; alol < (v).size() ; alol++){cout<<(v)[alol]<<' ';}cout << endl;}
# define ln '\n'
//# define T int_fast32_t
# define int ll
int n;
struct segmentTree
{
int N , Null_val;
vint t;
segmentTree(int _n)
{
t.resize(_n * 4 , 0);
N = _n;
}
void build(int v , int l , int r , vint &a)
{
if(l == r)
{
t[v] = a[l];
return;
}
int mid = (l + r) >> 1;
build((v << 1) , l , mid , a);
build((v << 1)|1 , mid + 1 , r , a);
t[v] = t[(v << 1)] + t[(v << 1)|1];
}
void upd(int v , int l , int r , int &val , int &pos)
{
if(l == r)
{
t[v] = val;
return;
}
int mid = (l + r) >> 1;
if(mid >= pos)upd((v << 1) , l , mid , val,pos);
else upd((v << 1)|1 , mid + 1 , r , val , pos);
t[v] = t[(v << 1)] + t[(v << 1)|1];
}
int ask(int v , int l , int r ,int ql , int qr)
{
if(ql <= l && r <= qr)
{
return t[v];
}
if(ql > r || l > qr)return Null_val;
int mid = (l + r) >> 1;
return ask((v << 1) , l , mid ,ql , qr) +
ask((v << 1)|1 , mid + 1 , r ,ql , qr);
}
};
const int maxN = 2e5 + 123;
segmentTree st(maxN);
class problem
{
public:
bool solveyaxin = true;
int n;
string s;
int q;
vector<vector<pair<int,int>>> que;
vector<int> res;
void __brute_force__() {
}
void __init__() {
que.clear();
;
}
void __read__() {
cin >> n;
cin >> s;
cin >> q;
que.resize(n);
res.resize(n);
// st = segmentTree(n);
fori(q) {
// cout << q << ' ' << n << ' ' <<i << endl;
int l , r;
cin >> l >> r;
l--;r--;
que[r].pb({l , i});
// cout << l << ' ' << r << endl;
};
}
void __ff__() {
}
void __proces__() {
vector<int>v;
for(int i = 0 ; i < n; i++) {
if(s[i] == 'T') {
v.pb(i);
} else {
int val = 1;
st.upd(1, 0 , n - 1 , i , val);
val = -1;
if(!v.empty()){
st.upd(1 , 0 , n -1 , i , val);
v.pop_back();
}
}
for(auto &[l , id] : que[i]) {
int p = ll(st.ask(1 , 0 , n - 1 , l , i));
int temp = 0;
res[id] = v.size();
// cout << v.size() << ' ' << res[id] << endl;
}
}
}
void __out__() {
fori(q) cout << res[i] << ln;
}
void solve() {
__init__();
__read__();
// cout << "sa" << endl;
__ff__();
if(!solveyaxin)__brute_force__();
else __proces__();
__out__();
}
};
signed main()
{
fastio;
int t = 1;
// #ifndef ONLINE_JUDGE
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
// freopen("log.txt", "w", stderr);
// #endif
// cout << 1 <<endl;
// cin >> t;
// cout << t << endl;
while(t--) {
problem pq;
pq.solve();
}
return 0;
}
