#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(ll i = a; i < ll(b); ++i)
#define trav(a, v) for(auto& a : v)
#define all(x) x.begin(), x.end()
#define sz(x) (ll)(x).size()
#define D(x) cerr << #x << " = " << x << endl
typedef long long ll;
typedef pair<ll, ll> pii;
typedef vector<ll> vi;
int main() {
cin.sync_with_stdio(false);
ll k,n;
ll totDist = 0;
vector<ll> points;
cin>>k>>n;
rep(i,0,n){
char a,b;
ll c,d;
cin>>a>>c>>b>>d;
if(a!=b){
points.push_back(c);
points.push_back(d);
totDist++;
}else{
totDist += abs(c-d);
}
}
ll bestDist = 1e18;
rep(i,0,points.size()){
ll dist = 0;
rep(j,0,points.size()) dist += abs(points[j]-points[i]);
bestDist = min(dist,bestDist);
}
totDist += bestDist;
cout<<totDist<<endl;
}
