#include <iostream>
#include <vector>
using namespace std;
inline void solve()
{
int n;
cin>>n;
string s;
cin>>s;
int q;
cin>>q;
bool vis[n]={};
while (q--)
{
int l,r;
cin>>l>>r;
l--;r--;
int cur=0;
int ans=0;
for (int i=l;i<=r;i++)
{
cur=cur+(s[i]=='T'?-1:1);
if (cur<0)
{
cur=0;
vis[i]=1;
}
}
cur=0;
for (int i=r;i>=l;i--)
{
if (vis[i]) continue;
cur=cur+(s[i]=='T'?-1:1);
if (cur<0)
{
cur=0;
vis[i]=1;
}
}
for (int i=l;i<=r;i++)
{
ans+=vis[i];
vis[i]=0;
}
cout<<ans<<endl;
}
}
int main()
{
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
int t=1;
for (int i=1;i<=t;i++)
{
solve();
}
}
