#include <bits/stdc++.h>
using namespace std;
const int N = 2e3 + 5;
int n, q;
string s;
bool mark[N];
vector <int> ans;
void readInput();
void solve();
void writeOutput();
int main() {
ios:: sync_with_stdio(0), cin.tie(0), cout.tie(0);
readInput();
solve();
writeOutput();
return 0;
}
void readInput() {
cin >> n >> s >> q;
}
void solve() {
for (int i = 0; i < q; i++) {
int l, r;
cin >> l >> r;
int res = 0, cnt = 0;
fill(mark, mark + n, false);
for (int j = --l; j < r; j++) {
cnt += (1 - 2 * (s[j] == 'T'));
if (cnt < 0)
cnt++, res++, mark[j] = true;
}
cnt = 0;
for (int j = --r; j >= l; j--) {
if (mark[j])
continue;
cnt += (1 - 2 * (s[j] == 'T'));
if (cnt < 0)
cnt++, res++;
}
ans.push_back(res);
}
}
void writeOutput() {
for (int x: ans)
cout << x << endl;
}
