#include <bits/stdc++.h>
using namespace std;
#define int long long
void solve(){
int k , n , ans = 1e18 + 7 , ek = 0;
cin >> k >> n;
vector < int > A,B;
vector < pair < int , int > > consider;
for(int i = 0;i<n;i++){
char c1,c2;
int p1,p2;
cin >> c1 >> p1;
cin >> c2 >> p2;
if(c1 == c2){
ek += abs(p1-p2);
}
else{
if(c1 == 'A')A.push_back(p1);
else B.push_back(p1);
if(c2 == 'A')A.push_back(p2);
else B.push_back(p2);
consider.push_back({p1,p2});
}
}
if(A.size() and B.size()){
sort(A.begin() , A.end());
sort(B.begin() , B.end());
//cout << "A : ";for(auto itr : A)cout << itr << " ";cout << endl;
//cout << "B : ";for(auto itr : B)cout << itr << " ";cout << endl;
pair < int , int > r1 , r2;
r1 = {A[((int)A.size()-1)/2] , A[(int)A.size()/2]};
r2 = {B[((int)B.size()-1)/2] , B[(int)B.size()/2]};
//cout << "r1 : " << r1.first << " " << r1.second << endl;
//cout << "r2 : " << r2.first << " " << r2.second << endl;
vector < int > cand;
if(r1.first > r2.first)swap(r1,r2);
if(r1.second >= r2.first)cand.push_back(r1.second);
else {
cand.push_back((r1.second + r2.first) / 2+2);
cand.push_back((r1.second + r2.first) / 2+1);
cand.push_back((r1.second + r2.first) / 2);
cand.push_back((r1.second + r2.first) / 2-1);
cand.push_back((r1.second + r2.first) / 2-2);
}
//cout << "cand : ";for(auto itr : cand)cout << itr << " ";cout << endl;
for(auto itr : cand){
int locans = 0;
for(auto itr1 : consider){
locans += abs(itr1.first - itr) + abs(itr1.second - itr) + 1;
}
//cout << itr << " : " << locans + ek << endl;
ans = min(ans , locans);
}
}
else ans = 0;
cout << ans + ek << endl;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int testcase = 1;//cin >> testcase;
while(testcase--)solve();
}
