n=int(input())
a=[]
sr=input()
for i in range(n):
    a.append(sr[i:i+1])
s=0
js=0
for i in range(n):
    if(a[i]=="V"):
        s=s+1
        js=js+1
    else:
        if(js>=3):
            s=s+(js-2)
        js=0
        if(a[i]=="X"):
            s=s-1
if(js>=3):
    s=s+(js-2)
print(s)
/**************************************************************
	Problem: 2002
	User: admin
	Language: Python
	Result: Accepted
	Time:621 ms
	Memory:34480 kb
****************************************************************/