#include<bits/stdc++.h>
using namespace std;
#define int long long
#define L(i,j,k) for(int i=(j);i<=(k);i++)
#define R(i,j,k) for(int i=(j);i>=(k);i--)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
const int MOD=1e16;
//essa porra da AC
void solve(){
int n,k;cin>>k>>n;
vector<int> evs;//lugar e tipo de evento
int dist=0;
vector<pair<int,int>> pevs;
L(i,0,n-1){
char c1,c2;
int a,b;
cin>>c1>>a>>c2>>b;
if(c1==c2){dist+=abs(a-b);continue;}
evs.push_back(a);
evs.push_back(b);
pevs.push_back({a,b});
dist++;
}
sort(all(evs));
int distaux=0;
if(k==1){
int ponte=evs[sz(evs)/2];
for(auto [a,b]:pevs)dist+=abs(a-ponte)+abs(b-ponte);
//for(auto a:evs)dist+=abs(a-ponte);
cout<<dist;
return;
}
int distminaux=MOD;
if(sz(evs)==0)distminaux=0;
L(i,0,sz(evs)-1){
L(j,i+1,sz(evs)-1){
distaux=0;
for(auto [a,b]:pevs){
distaux+=min(abs(a-evs[i])+abs(b-evs[i]),abs(a-evs[j])+abs(b-evs[j]));
}
distminaux=min(distaux,distminaux);
}
}
cout<<dist+distminaux;
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);
solve();
}
