#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int Nmax = 1e5 + 5;
struct segment
{
int x, y;
bool operator < (const segment &other) const
{
return x + y < other.x + other.y;
}
};
vector<segment> v;
map<int,int> mp;
ll dp1[Nmax], dp2[Nmax];
ll ans = 0;
int ord[2*Nmax];
struct AIB
{
int a[2*Nmax];
ll b[2*Nmax];
int ub(int x) { return (x&(-x)); }
void clear()
{
memset(a, 0, sizeof(a));
memset(b, 0, sizeof(b));
}
void upd(int pos, int A, int B)
{
for(; pos<=mp.size(); pos+=ub(pos))
a[pos] += A, b[pos] += B;
}
ll query(int Pos)
{
int A = 0, pos = Pos; ll B = 0;
for(; pos; pos-=ub(pos))
A += a[pos], B += b[pos];
return (ll) A * ord[Pos] + B;
}
void update(int X, int Y)
{
int x = mp[X], y = mp[Y];
upd(y, 1, -Y);
upd(1, -1, X);
upd(x, 1, -X);
}
} aib;
void init()
{
sort(v.begin(), v.end());
int cnt = 0;
for(auto &it : mp)
{
it.second = ++cnt;
ord[cnt] = it.first;
}
}
void prefix()
{
aib.clear();
int i, id = 1;
for(i=0; i<v.size(); ++i)
{
aib.update(v[i].x, v[i].y);
while(id<mp.size() && aib.query(id) >= aib.query(id+1)) ++id;
dp1[i] = aib.query(id);
}
}
void suffix()
{
aib.clear();
int i, id = mp.size();
for(i=v.size()-1; i>=0; --i)
{
aib.update(v[i].x, v[i].y);
while(id>1 && aib.query(id) >= aib.query(id-1)) --id;
dp2[i] = aib.query(id);
}
}
int main()
{
// freopen("input", "r", stdin);
int i, N, K, x, y;
char tip1, tip2;
cin >> K >> N;
for(i=1; i<=N; ++i)
{
cin >> tip1 >> x >> tip2 >> y;
if(x > y) swap(x, y);
ans += y - x;
if(tip1 != tip2)
{
++ans;
v.push_back({x, y});
mp[x] = 1; mp[y] = 1;
}
}
init();
prefix();
suffix();
K = min(K, (int) mp.size());
K = min(K, (int) v.size());
ll best;
if(K == 1) best = dp1[v.size()-1];
else
{
best = 1e18;
for(i=0; i<(int) v.size()-1; ++i) best = min(best, dp1[i] + dp2[i+1]);
}
cout << 2 * best + ans << '\n';
return 0;
}
