#include <cmath>
#include <functional>
#include <fstream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <map>
#include <list>
#include <time.h>
#include <math.h>
#include <random>
#include <deque>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <cassert>
#include <bitset>
#include <sstream>
#include <chrono>
#include <cstring>
#include <numeric>
using namespace std;
#define int long long
const int INF = (int)1e18 + 7;
pair<int, int> _rd_()
{
string s;
int i;
cin >> s >> i;
assert(s == "A" || s == "B");
return { s == "B", i };
}
const int N = (int)1e5 + 7;
int k;
int n;
int extra;
pair<int, int> c1[N], c2[N];
signed main()
{
#ifdef ONPC
FILE* stream;
freopen_s(&stream, "input.txt", "r", stdin);
#else
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#endif
cin >> k >> n;
assert(k == 1);
{
int y = 0;
for (int i = 1; i <= n; i++)
{
c1[i] = _rd_();
c2[i] = _rd_();
if (c1[i].first == c2[i].first)
{
extra += abs(c1[i].second - c2[i].second);
continue;
}
y++;
c1[y] = c1[i];
c2[y] = c2[i];
}
n = y;
}
if (n == 0)
{
cout << extra << "\n";
return 0;
}
vector<int> coords;
for (int i = 1; i <= n; i++)
{
coords.push_back(c1[i].second);
coords.push_back(c2[i].second);
}
nth_element(coords.begin(), coords.begin() + n - 1, coords.end());
int su = 0;
for (int i = 0; i < 2 * n; i++)
{
su += abs(coords[i] - coords[n - 1]);
}
cout << su + extra + n << "\n";
return 0;
}
