from collections import defaultdict
n = int(input())
p = list(map(int,input().split()))
d = defaultdict(int)
for i in range(n):
    d[p[i]] = i
ans = 0
for i in range(n):
    if p[i] > i + 1:
            plus = -1
    elif p[i] < i + 1:
            plus = 1
    else:
        continue
    while p[i] != i + 1:
        idx = d[p[i] + plus]
        d[p[i] + plus] , d[p[i]] =d[p[i]],  d[p[i] + plus]  
        p[i] ,p[idx] = p[idx] ,p[i]
        ans += 1
print(ans)