import java.util.*;
class Main {
public static void main (String[]args) {
Scanner scan = new Scanner (System.in);
int allowedBridges = scan.nextInt();
int citizenNumber = scan.nextInt();
long previousAdding = 0;
ArrayList<Integer> locations = new ArrayList<Integer>();
for (int i = 0; i < citizenNumber; i++) {
String line = scan.next();
char startZone = line.charAt(0);
int index = 0;
for (int j = 1; j < line.length(); j++) {
if (line.charAt(j) == 'A' || line.charAt(j) == 'B') {
index = j;
break;
}
}
int startLocation = Integer.valueOf(line.substring(1, index));
char endZone = line.charAt(index);
int endLocation = Integer.valueOf(line.substring(index + 1));
if (startZone == endZone) {
previousAdding += Math.abs(endLocation - startLocation);
continue;
}
locations.add(startLocation);
locations.add(endLocation);
}
/*
* If we are only able to build one bridge, we should
* build it at the median of all start and end locations.
* After find the median, we can calculate the answer
* by looping through all values and adding the previously
* calculated value for locations in the same zone.
*/
if (allowedBridges == 1) {
Collections.sort(locations);
int size = locations.size();
int median = locations.get(size / 2 - 1);
long answer = 0;
for (int i = 0; i < locations.size(); i++) {
answer += Math.abs(locations.get(i) - median);
}
answer += locations.size() / 2;
answer += previousAdding;
System.out.println(answer);
}
else {
System.out.println(100);
}
}
}
