#include <iostream>

using namespace std;

int main()
{
   int n, s = 0;
   string b;
   cin >> n;
   int pos = 1;
    for(int i = 0; i < n; ++i){
        cin >> b;
        if(b[0] =='A'||b[0]=='P'||b[0]=='O'||b[0]=='R'){
            s+=abs(pos - 1);
            pos = 1;
        }
        else
            if(b[0] =='B'||b[0]=='M'||b[0]=='O'||b[0]=='S'){
                s+=abs(pos - 2);
                pos = 2;
            }
        else{
            s+=abs(pos - 3);
            pos = 3;
        }
    }
    cout << s;
    return 0;
}