WA #4

#include<bits/stdc++.h>
#define for1(a,b,c) for(auto a=b;a<=c;++a)
#define for2(a,b,c) for(auto a=b;a>=c;--a)
#define for3(a,b) for(auto a:b)
//#define for4(a,b,c) for(auto [a,b]:c)
#define for5(a,b,c,d) for(auto a=b;a<=c;a+=d)
#define for6(a,b,c,d) for(auto a=b;a>=c;a-=d)
#define int long long
using namespace std;
using ll=long long;
using ld=long double;
const int N=500005;
int lg[N],rg[N],lh[N],rh[N];
signed main(){
//	freopen("photo.in","r",stdin);
//	freopen("photo.out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0);
	int n;
	cin>>n;
	string s;
	cin>>s;
	stack<int> st;
	memset(lg,-1,sizeof(lg));
	memset(lh,-1,sizeof(lh));
	fill(rg,rg+n,n);
	fill(rh,rh+n,n);
	while(!st.empty()) st.pop();
	for1(i,0,n-1){
		if(s[i]=='G'){
			while(!st.empty()) rg[st.top()]=i,st.pop();
		}
		st.push(i);
	}
	while(!st.empty()) st.pop();
	for2(i,n-1,0){
		if(s[i]=='G'){
			while(!st.empty()) lg[st.top()]=i,st.pop();
		}
		st.push(i);
	}
	while(!st.empty()) st.pop();
	for1(i,0,n-1){
		if(s[i]=='H'){
			while(!st.empty()) rh[st.top()]=i,st.pop();
		}
		st.push(i);
	}
	while(!st.empty()) st.pop();
	for2(i,n-1,0){
		if(s[i]=='H'){
			while(!st.empty()) lh[st.top()]=i,st.pop();
		}
		st.push(i);
	}
	while(!st.empty()) st.pop();
//	for1(i,0,n-1){cout<<"i:"<<i<<",s[i]:"<<s[i]<<",lg[i]:"<<lg[i]<<",lh[i]:"<<lh[i]<<",rg[i]:"<<rg[i]<<",rh[i]:"<<rh[i]<<'\n';for1(j,1,1000000){cout<<"";}}
	int ans=0;
	for1(i,0,n-1){
		if(s[i]=='G')
			ans+=max(0ll,(i-lg[i])*(rg[i]-i)-3);
		if(s[i]=='H')
			ans+=max(0ll,(i-lh[i])*(rh[i]-i)-3);
	}
	cout<<ans;
    return 0;
}