#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#pragma GCC optimize("Ofast,unroll-loops")
#define ll long long
#define all(x) x.begin(), x.end()
#define ld long double
#define pii pair<int, int>
using namespace std;
using namespace __gnu_pbds;
template<class T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int INF = 1e9 + 7;
const int MAXN = 1e5 + 5;
struct st{
bool a;
bool b;
int x;
int y;
};
int n;
vector<st> a;
long long calc(int pos){
ll d = 0;
for(int i = 1; i <= n; i++){
if(a[i].a != a[i].b){
if(pos < a[i].x) d += (a[i].x - pos) * 2;
if(pos > a[i].y) d += (pos - a[i].y) * 2;
d += a[i].y - a[i].x + 1;
}
else d += a[i].y - a[i].x;
}
return d;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
// ifstream cin("input.txt");
// ofstream cout("output.txt");
int k;
cin >> k >> n;
a.resize(n + 1);
{
char a1, b1;
for(int i = 1; i <= n; i++){
cin >> a1 >> a[i].x >> b1 >> a[i].y;
a[i].a = a1 - 'A';
a[i].b = b1 - 'A';
if(a[i].x > a[i].y) swap(a[i].x, a[i].y);
}
}
int l = 0, r = 1e9;
ll ans = 1e18;
while(l <= r){
int m1 = l + (r - l) / 3;
int m2 = r - (r - l) / 3;
ans = min(ans, calc(m1));
ans = min(ans, calc(m2));
if(calc(m1) < calc(m2)){
r = m2 - 1;
}
else{
l = m1 + 1;
}
}
for(int i = l; i <= r; i++){
ans = min(ans, calc(i));
}
cout << ans << endl;
}
