#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
const int mxN = 5e5 + 5;
ll n,qq,ans[mxN];
pair<ll,pair<ll,ll>> q[mxN];
char ch[mxN];
struct segtree{
vector<ll> v,v1;
ll sz = 1;
void init(){
while(sz < n) sz *= 2;
v.assign(2 * sz, 0LL);
v1.assign(2 * sz, 0LL);
}
void set(ll val, ll l, ll r, ll x, ll lx, ll rx){
if(lx >= r or rx <= l) return;
if(lx >= l and rx <= r){
v1[x] += val;
v[x] += val;
return;
}
ll mid = lx + (rx - lx) / 2;
set(val, l, r, 2 * x + 1, lx, mid);
set(val, l, r, 2 * x + 2, mid, rx);
v[x] = min(v[2 * x + 1], v[2 * x + 2]) + v1[x];
}
void set(ll val, ll l, ll r){
set(val, l, r, 0, 0, sz);
}
ll find(ll l, ll r, ll x, ll lx, ll rx){
if(lx >= r or rx <= l) return 1e16;
if(lx >= l and rx <= r) return v[x];
ll mid = lx + (rx - lx) / 2;
return (min(find(l, r, 2 * x + 1, lx, mid), find(l, r, 2 * x + 2, mid, rx)) + v1[x]);
}
ll find(ll l, ll r){
return find(l, r, 0, 0, sz);
}
};
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n;
segtree s;
s.init();
for(int i = 0; i < n; i++){
cin >> ch[i];
}
cin >> qq;
for(int i = 0; i < qq; i++){
cin >> q[i].second.first >> q[i].first;
q[i].first--;
q[i].second.first--;
q[i].second.second = i;
}
sort(q, q + qq);
vector<ll> st;
ll l1 = 0;
for(int i = 0; i < qq; i++){
ll l = q[i].second.first, r = q[i].first;
// cout << l << ' ' << r << '\n';
while(l1 <= r){
if(ch[l1] == 'T') st.pb(l1);
else{
s.set(1, l1, n);
if(!st.empty()){
s.set(-1, st[st.size() - 1], n);
st.pop_back();
}
}
l1++;
// cout << l1 << '\n';
}
ll x,sz = st.size();
auto it = lower_bound(st.begin(), st.end(), l);
if(it == st.end()) x = 0;
else x = sz - (it - st.begin());
// cout << s.find(l - 1, l) << '\n';
if(l) ans[q[i].second.second] = max(0LL, -(s.find(l, r) - s.find(l - 1, l))) + x;
else ans[q[i].second.second] = max(0LL, -(s.find(l, r))) + x;
}
for(int i = 0; i < qq; i++) cout << ans[i] << '\n';
}
