#include <fstream>
#include <iostream>

using namespace std;
ofstream fout("furnici.out");
int main()
{
    char dir;
    int i,n,x,rez=0,l;
    freopen("furnici.in", "r", stdin);
    scanf("%d %d",&l,&n);
    for(i=0;i<n;i++)
    {
        scanf("%d %c\n",&x,&dir);
        if(dir=='S')
            rez=max(rez,x);
        else
            rez=max(rez,l-x);
    }
    fout<<rez;
    return 0;
}