#include <vector>
#include <iostream>
#include <cassert>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <set>
#include <map>
#include <string>
#include <unordered_map>
#include <functional>
#include <bitset>
#include <sstream>
using namespace std;
using int64 = long long;
int N, M, K;
vector<pair<int64, int64>> segments;
vector<int64> X;
vector<int64> vec;
map<int64, int> idx;
int64 dist(int64 x, pair<int64, int64> & s) {
if (s.second < x) {
return 2 * (x - s.second);
} else if (s.second >= x && s.first <= x) {
return 0;
} else {
return 2 * (s.first - x);
}
}
int64 solve1brute() {
int64 res = (1LL<<60);
for (auto & x : vec) {
int64 cur = 0;
for (auto & s : segments) {
cur += dist(x, s);
}
res = min(res, cur);
}
return res;
}
// optimum right bridge for left bridges in [l, r] is
// in [optl, optr]
vector<int64> dp;
void rec(int l, int r, int optl, int optr) {
if (l > r)
return;
int m = (l + r) >> 1;
int opt = -1;
int64 bst = (1LL<<60);
for (int i = max(m + 1, optl); i <= optr; i++) {
// Compute cost(m, opt)
int64 cur = 0;
for (auto & s: segments) {
cur += min(dist(vec[m], s), dist(vec[i], s));
}
if (cur < bst) {
bst = cur;
opt = i;
}
}
assert(opt != -1);
dp[m] = bst;
rec(l, m - 1, optl, opt);
rec(m + 1, r, opt, optr);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int64 res = 0;
cin >> K >> N;
set<int64> uniq;
for (int i = 0; i < N; i++) {
char z1, z2;
int x1, x2;
cin >> z1 >> x1 >> z2 >> x2;
res += abs(x1 - x2);
if (z1 != z2) {
segments.emplace_back(min(x1, x2), max(x1, x2));
uniq.insert(x1);
uniq.insert(x2);
}
}
uniq.insert(-(1<<30));
uniq.insert((1LL<<31));
if (!size(segments)) {
cout << res << "\n";
return 0;
}
vec = vector<int64>(begin(uniq), end(uniq));
N = size(vec);
for (int i = 0; i < N; i++) {
idx[vec[i]] = i;
}
M = size(segments);
res += M; // every crossed a bridge
// need at least one bridge;
dp.assign(N + 2, (1LL<<60));
rec(0, N - 2, 1, N - 1);
if (K == 1) {
cout << res + dp[0] << "\n";
} else {
cout << res + (*min_element(begin(dp) + 1, begin(dp) + N - 2)) << "\n";
}
return 0;
}
