#include <bits/stdc++.h>
using namespace std;
#define ll long long
struct Citizen {
int sideFrom, sideTo;
ll from, to;
};
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int K, N;
cin >> K >> N;
vector<Citizen> citizens(N);
vector<ll> bridge_candidates;
for (int i = 0; i < N; ++i) {
string s;
cin >> s;
citizens[i].sideFrom = (s[0] == 'A' ? 0 : 1);
ll num1 = 0, j = 1;
while (isdigit(s[j])) num1 = num1 * 10 + (s[j++] - '0');
citizens[i].from = num1;
citizens[i].sideTo = (s[j++] == 'A' ? 0 : 1);
ll num2 = 0;
while (j < s.size()) num2 = num2 * 10 + (s[j++] - '0');
citizens[i].to = num2;
if (citizens[i].sideFrom != citizens[i].sideTo) {
// Add both positions for potential bridge
bridge_candidates.push_back(citizens[i].from);
bridge_candidates.push_back(citizens[i].to);
}
}
sort(bridge_candidates.begin(), bridge_candidates.end());
ll ans = LLONG_MAX;
for (ll bridge : bridge_candidates) {
ll total = 0;
for (const auto& c : citizens) {
if (c.sideFrom == c.sideTo) {
total += abs(c.from - c.to);
} else {
// Cost using bridge at `bridge`
ll temp = abs(c.from - bridge) + 1 + abs(c.to - bridge);
total += temp;
}
}
ans = min(ans, total);
}
cout << ans << '\n';
return 0;
}
