/*
Code written by Talant I.D.
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
#define precision(n) fixed << setprecision(n)
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define mp make_pair
#define eps (double)1e-9
#define PI 2*acos(0.0)
#define endl "\n"
#define sz(v) int((v).size())
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define OK cout << "OK" << endl;
const int mod = 998244353;
ll mode(ll a) {
a %= mod;
if (a < 0) a += mod;
return a;
}
ll subt(ll a, ll b) {
return mode(mode(a)-mode(b));
}
ll add(ll a, ll b) {
return mode(mode(a)+mode(b));
}
ll mult(ll a, ll b) {
return mode(mode(a)*mode(b));
}
ll binpow(ll a, ll b) {
ll res = 1;
while (b) {
if (b&1) res = mult(res, a);
a = mult(a, a);
b >>= 1;
}
return res;
}
int main() {
do_not_disturb
int k, n;
cin >> k >> n;
ll sum = 0;
vector <ll> v;
for (int i = 0; i < n; i++) {
char a, b;
int aa, bb;
cin >> a >> aa >> b >> bb;
if (a == b) {
sum += abs(aa-bb);
}
else {
v.pb(aa); v.pb(bb);
}
}
sort(all(v));
sum += sz(v)/2;
for (int i = 0; i < sz(v)/2; i++) sum -= v[i];
for (int i = sz(v)/2; i < sz(v); i++) sum += v[i];
cout << sum;
return 0;
}
