from itertools import accumulate
n=int(input())
a=list(map(int,input().split()))
f=[0]*n
for i in range(1,n):
    if a[i]-a[i-1]==1:
        f[i]=1
f=[0]+f
F=list(accumulate(f))
#print(f)
ans=0
for size in range(2,n+1):
    #print('今のサイズ'+str(size))
    for i in range(n+1-size):
        cnt=F[i+size]-F[i]
        #print(cnt)
        if cnt==size:
            ans+=1
        elif cnt==size-1 and f[i+1]==0:
            ans+=1
        else:
            pass
        #print('ansは'+str(ans))
print(ans)