#include <iostream>
#include <fstream>
#include <iomanip>
#include <vector>
#include <set>
#include <map>
#include <cstring>
#include <string>
#include <cmath>
#include <cassert>
#include <ctime>
#include <algorithm>
#include <sstream>
#include <list>
#include <queue>
#include <deque>
#include <stack>
#include <cstdlib>
#include <cstdio>
#include <iterator>
#include <functional>
#include <unordered_set>
#include <unordered_map>
#include <stdio.h>
#include <bitset>
#include <cstdint>
#include <cassert>
#include <functional>
#include <complex>
#include <climits>
#include <random>
using namespace std;
#define ll long long
#define pb push_back
#define ull unsigned long long
#define F first
#define S second
#define all(v) v.begin(), v.end()
struct bruh{
char A, B;
ll x, y;
} a[20005];
void solve(){
int k, n;
cin >> k >> n;
ll ans = INT_MAX;
vector<ll> v;
for(int i = 1; i <= n; i++){
char A, B;
ll x, y;
cin >> A >> x;
cin >> B >> y;
a[i].A = A, a[i].B = B;
a[i].x = x, a[i].y = y;
v.pb(y);
}
sort(all(v));
for(auto i : v){
ll bridge = i;
ll cnt = 0LL;
for(int j = 1; j <= n; j++){
ll x = a[j].x;
ll y = a[j].y;
if(a[j].A == a[j].B){
cnt += abs(x - y);
continue;
}
cnt += abs(x - bridge) + abs(bridge - y) + 1LL;
}
ans = min(ans, cnt);
}
cout << ans;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL), cout.tie(NULL);
int xach = 1;
//cin >> xach;
while(xach--) solve();
}
/*
*
*/
