N = int(input())
a = list(map(int,input().split()))

def checkALL(numList):
    for i in range(len(numList)):
        if numList[i] != i+1:
            return False
    
    return True

cnt = 0
for i in range(len(a)):
    if checkALL(a):
        break
    elif a[a.index(i+1)] == i:
        continue
    else:
        cnt += 1
        del a[a.index(i+1)]
        a.insert(i, i+1)
    # print(a)

print(cnt)