#include <bits/stdc++.h>
using namespace std;
#define pr pair<int, int>
#define ll long long
#define pb push_back
#define f first
#define s second
priority_queue<int> lft;
priority_queue<int, vector<int>, greater<int>> rht;
bool comp(pr a, pr b){
return a.f+a.s<b.f+b.s;
}
void dataInsert(int elem, ll &lsum, ll &rsum){
int mid=(int)lft.size()?lft.top(): 1e9;
if(elem>mid) {rht.push(elem); rsum+=elem;}
else {lft.push(elem); lsum+=elem;}
// move between lft & rht;
if(rht.size()+1<lft.size()){ //r to l
int temp=lft.top();
rht.push(temp); lft.pop();
rsum+=temp; lsum-=temp;
}
else if(lft.size()<rht.size()){
int temp=rht.top();
lft.push(temp); rht.pop();
lsum+=temp; rsum-=temp;
}
}
int main(){
int nb, n; cin>>nb>>n;
vector<pr> nlist;
ll dist1=0;
for (int i=0; i<n; i++){
char s1, num1, s2, num2;
cin>>s1>>num1>>s2>>num2;
if(s1==s2) dist1+=abs(num1-num2);
else{
nlist.push_back({num1, num2});
}
}
dist1+=(int)nlist.size();
sort(nlist.begin(), nlist.end(), comp);
ll lsum, rsum;
lsum=0; rsum=0;
vector<int> pfix(100100, 0);
for (int i=0; i<(int)nlist.size(); i++){
dataInsert(nlist[i].f, lsum, rsum);
dataInsert(nlist[i].s, lsum, rsum);
pfix[i]=rsum-lsum;
}
ll ans=pfix[(int)nlist.size()-1];
if(nb==2){
// for nd=2 case
while(!lft.empty()) lft.pop();
while(!rht.empty()) rht.pop();
lsum=0; rsum=0;
for (int i=(int)nlist.size()-1; i>=0; i--){
dataInsert(nlist[i].f, lsum, rsum);
dataInsert(nlist[i].s, lsum, rsum);
ans=min(ans, pfix[i-1]+rsum-lsum);
}
}
cout<<ans+dist1; return 0;
}
