#include<bits/stdc++.h>
#define ll long long
#define ldb long double
#define fi first
#define se second
#define sza(a) (int)a.size()
#define pir pair<int,int>
#define pirll pair<ll,ll>
using namespace std;
const int maxn = 1e5 + 5;
bool type[maxn][2];
int pos[maxn][2];
void input(int n){
for (int i = 1 ; i <= n ; i++){
for (int id = 0 ; id <= 1 ; id++){
char c;int p;
cin >> c >> p;
type[i][id] = (c == 'A') ? 0 : 1;
pos[i][id] = p;
}
}
}
namespace sub1{
bool check(int n,int k){
return (k == 1) && (n <= 1000);
}
ll calc(int x,int n){
ll t = 0;
for (int i = 1 ; i <= n ; i++)
if (type[i][0] == type[i][1]) t += abs(pos[i][0] - pos[i][1]);
else t += abs(pos[i][0] - x) + abs(pos[i][1] - x) + 1;
return t;
}
ll solve(int n,int k){
ll res = LLONG_MAX;
for (int i = 1 ; i <= n ; i++)
res = min(res,min(calc(pos[i][0],n),calc(pos[i][1],n)));
return res;
}
}
namespace sub3{
bool check(int n,int k){
return (k == 2 && n <= 100);
}
ll calc(int x,int y,int n){
ll t = 0;
for (int i = 1 ; i <= n ; i++){
if (type[i][0] == type[i][1]) t += abs(pos[i][0] - pos[i][1]);
else{
ll x1 = abs(pos[i][0] - x) + abs(pos[i][1] - x);
ll x2 = abs(pos[i][0] - y) + abs(pos[i][1] - y);
t += min(x1,x2) + 1;
}
}
return t;
}
ll solve(int n,int k){
vector <int> tmp;
ll res = LLONG_MAX;
for (int i = 1 ; i <= n ; i++){
tmp.push_back(pos[i][0]);
tmp.push_back(pos[i][1]);
}
sort(tmp.begin(),tmp.end());
for (int x : tmp)
for (int y : tmp)
if (x <= y) res = min(res,calc(x,y,n));
return res;
}
}
namespace sub2{
bool check(int n,int k){
return (k == 1);
}
bool byR(pir x,pir y){
return (x.se < y.se) || (x.se == y.se && x.fi < y.fi);
}
vector <pir> L,R;
ll simplify(int n){
int M = n;ll res = 0;
for (int i = 1 ; i <= n ; i++){
if (type[i][0] == type[i][1])
res += abs(pos[i][0] - pos[i][1]);
else{
if (pos[i][0] > pos[i][1]) swap(pos[i][0],pos[i][1]);
L.push_back({pos[i][0],pos[i][1]});
R.push_back({pos[i][0],pos[i][1]});
}
}
return res;
}
ll prelen[maxn],pre[maxn];
ll suflen[maxn],suf[maxn];
void prepare(){
sort(L.begin(),L.end(),byR);
sort(R.begin(),R.end());
for (int i = 0 ; i < L.size() ; i++){
prelen[i] = ((!i) ? 0 : prelen[i - 1]) + L[i].se - L[i].fi;
pre[i] = ((!i) ? 0 : pre[i - 1]) + L[i].se + L[i].fi;
}
for (int i = R.size() - 1; i >= 0; i--){
suflen[i] = suflen[i + 1] + R[i].se - R[i].fi;
suf[i] = suf[i + 1] + R[i].fi + R[i].se;
}
}
ll calc(int x,ll C){
ll res = C;
if (x > L[0].se){
int l = 0,r = L.size() - 1,vt = 0;
while (l <= r){
int w = (l + r)/2;
if (L[w].se < x){
vt = w;
l = w + 1;
}
else r = w - 1;
}
res -= prelen[vt];
res += 2*(ll)x*(ll)(vt + 1) - pre[vt];
}
if (x < R.back().fi){
int l = 0,r = R.size() - 1,vt = R.size() - 1;
while (l <= r){
int w = (l + r)/2;
if (R[w].fi > x){
vt = w;
r = w - 1;
}
else l = w + 1;
}
res -= suflen[vt];
res += suf[vt] - 2*(ll)x*(ll)(R.size() - vt);
}
res += L.size();
return res;
}
ll solve(int n,int k){
ll res = simplify(n);
if (!L.size()) return res;
prepare();
ll T = LLONG_MAX,C = 0;
for (pir t : L)
C += t.se - t.fi;
for (int i = 1 ; i <= n ; i++)
T = min(T,min(calc(pos[i][0],C),calc(pos[i][1],C)));
return res + T;
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);cout.tie(0);
// freopen("B.inp","r",stdin);
// freopen("B.out","w",stdout);
int k,n;
cin >> k >> n;
input(n);
if (sub1::check(n,k))
cout << sub1::solve(n,k) << "\n";else
if (sub2::check(n,k))
cout << sub2::solve(n,k) << "\n";else
;
if (sub3::check(n,k))
cout << sub3::solve(n,k);else
return 0;
}
