#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define re exit(0);
#define left __left__
#define right __right__
const int maxn = 100009;
int k,n,cnt;
ll offset = 0;
pair <int,int> segment[maxn];
ll sumleft,sumright;
multiset <int> left,right;
ll cost1[maxn],cost2[maxn];
void rebalance() {
int len = left.size() + right.size();
while (left.size() < (len + 1) / 2) {
sumleft += *right.begin();
left.insert(*right.begin());
sumright -= *right.begin();
right.erase(right.begin());
}
while (left.size() > (len + 1) / 2) {
sumright += *left.rbegin();
right.insert(*left.rbegin());
auto x = left.end();x --;
sumleft -= *x;
left.erase(x);
}
}
void add(int val) {
if (right.size() && *right.begin() <= val) {
right.insert(val);
sumright += val;
}
else {
left.insert(val);
sumleft += val;
}
rebalance();
}
ll getcost() {
int median = *left.rbegin();
ll ret = 0;
ret += 1ll * median * left.size() - sumleft;
ret += sumright - 1ll * median * right.size();
return ret;
}
void solve() {
sort(segment + 1,segment + 1 + n,[] (pair <int,int> a,pair <int,int> b) {
return a.first + a.second < b.first + b.second;
});
for (int i = 1;i <= n;i++) {
add(segment[i].first);
add(segment[i].second);
cost1[i] = getcost();
}
left.clear(),right.clear();
sumleft = sumright = 0;
for (int i = n;i >= 1;i--) {
add(segment[i].first);
add(segment[i].second);
cost2[i] = getcost();
}
ll res = cost1[n];
if (k == 2) {
for (int i = 1;i < n;i++) res = min(res,cost1[i] + cost2[i + 1]);
}
cout << res + offset;
}
int main() {
ios_base::sync_with_stdio(0);cin.tie(nullptr);
cin >> k >> n;
for (int i = 1;i <= n;i++) {
char _1,_2;int __1,__2;
cin >> _1 >> __1 >> _2 >> __2;
if (_1 == _2) offset += abs(__2 - __1);
else {
segment[++cnt] = {__1,__2};
offset++;
if (segment[cnt].first > segment[cnt].second) swap(segment[cnt].first,segment[cnt].second);
}
}
n = cnt;
if (n == 0) {
cout << offset;
re;
}
solve();
}
/*
Aiming:
==
+++++***
+:::::-=*
------=
========== ================== --:--== ============--
========== ==-------=--:=--==== ---==++ ===========--====-=
==--======== ==--================= =:::-=+ ==============----====
==:-========= ===:=== ======= =::--=+ ======== ==--====
==--========== ==-:=== ======= -:::-:= ======= =======
==--:== ======= ==--=== ======= =-:::-= ======= =======
=-.-=== ======= ==-==== ======= *:::----* ======= =======
==--:== ======= ==-================== +-:::::-+ ====== =======
==-:-=== ======= ==--================ *=-:::::-= ======= =======
==---=============== ==--============= +--::---==* ====--= =======
===--================= ==:-=== =:-::::--=+ ====-=== =======
==.-=================== ==--=== =::::::---+ ====---== =========
==---== ======= ======= +-:---=====+ ==-===--==============
======= ======= ======= =-:::::::--=+ =--=-=============
======== ======= ======= =--::::::--=+ =============
***++++++++++*****
*/
