#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define endl "\n";
#define all(x) x.begin(), x.end()
const ll MOD = 1e9+7;
#define int long long
void solve() {
int k, n; cin >> k >> n;
if (k == 2) {
cout << -1 << endl;
return;
}
vector<int> start;
vector<int> end;
ll sum = 0;
ll initLoss = 0;
int nonTriv = 0;
for (int i = 0; i < n; i++) {
char a; int s; char b; int e;
cin >> a >> s >> b >> e;
if (a == b) {
sum += abs(e-s);
} else {
nonTriv++;
if (s > e) {
swap(s, e);
}
sum += abs(e-s);
sum++;
initLoss += s;
start.push_back(s);
end.push_back(e);
}
}
sort(all(start));
sort(all(end));
ll minLoss = initLoss;
ll curLoss = initLoss;
int left = 0;
int right = nonTriv;
int sIndex = 0;
int eIndex = 0;
for (int i = 0; i < n; i++) {
if (i > 0) {
curLoss -= right;
}
while (sIndex < start.size() && start[sIndex] <= i) {
right--;
sIndex++;
}
while (eIndex < end.size() && end[eIndex] < i) {
left++;
eIndex++;
}
curLoss += left;
minLoss = min(minLoss, curLoss);
}
cout << sum + minLoss*2 << endl;
}
signed main() {
ios::sync_with_stdio(0); cin.tie(NULL);
//freopen("example.in", "r", stdin);
// freopen("hayfeast.out", "w", stdout);
int t = 1; // cin >> t;
while (t--) {
solve();
}
}
