def Run_Length_Encoding(S):
    """ランレングス圧縮

    S: 文字列
    """
    if not S:
        return []

    R=[[S[0],1]]

    for i in range(1,len(S)):
        if R[-1][0]==S[i]:
            R[-1][1]+=1
        else:
            R.append([S[i],1])

    return R

#==================================================
N=int(input())
A=list(map(int,input().split()))
B=[A[i+1]-A[i] for i in range(N-1)]

X=0
for d,k in Run_Length_Encoding(B):
    if d==1:
        X+=k*(k+1)//2

print(X)