n=int(input())
a=[]
for i in range(n):
    s=input()
    if(s[0]=="A" or s[0]=="P" or s[0]=="O" or s[0]=="R"):
        a.append(0)
    elif(s[0]=="B" or s[0]=="M" or s[0]=="S"):
        a.append(1)
    else:
        a.append(2)
t=0
for i in range(n):
    if(i+1<n):
        t=t+abs(a[i]-a[i+1])
print(t)