AB - point 1, BA - point -1. Max point ?

#include <bits/stdc++.h>
#define task "TESTCODE"
using namespace std;
const int N = 1e6;
string s;
int n, dp[N + 1][2];
void read()
{
    cin >> n >> s;
    s = ';' + s;
}
void solve()
{
    memset(dp, -1, sizeof(dp));
    if (s[1] != 'a')
    {
        dp[1][1] = 0;
    }
    if (s[1] != 'b')
    {
        dp[1][0] = 0;
    }
    for (int i = 2; i <= n; ++ i)
    {
        if (s[i] != 'b')
        {
            dp[i][0] = max(dp[i-1][0], dp[i-1][1] - 1);
        }
        if (s[i] != 'a')
        {
            dp[i][1] = max(dp[i-1][1], dp[i-1][0] + 1);
        }
    }
    cout << max(dp[n][0], dp[n][1]);
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    //freopen(task".INP", "r", stdin);
    //freopen(task".OUT", "w", stdout);
    int t = 1;
    bool typetest = false;
    if (typetest)
    {
        cin >> t;
    }
    for (int _ = 1; _ <= t; ++ _ )
    {
        read();
        solve();
    }
    return 0;
}