import sys
readline=sys.stdin.readline

N=int(readline())
E=[int(readline()) for i in range(N)]
mod=10**9+7
dp=[[0]*4 for i in range(4)]
for i in range(2):
    for j in range(2):
        for k in range(2):
            if (i,j,k)==(1,1,1) or (j,k)==(0,0):
                e=0
            else:
                e=1
            if E[1]==e:
                dp[i*2+j][j*2+k]+=1
for e in E[2:-1]:
    prev=dp
    dp=[[0]*4 for i in range(4)]
    for i in range(4):
        for j in range(2):
            for k in range(2):
                for l in range(2):
                    if (j,k,l)==(1,1,1) or (k,l)==(0,0):
                        ee=0
                    else:
                        ee=1
                    if e==ee:
                        dp[i][k*2+l]+=prev[i][j*2+k]
                        dp[i][k*2+l]%=mod
for i in range(2):
    for j in range(2):
        for k in range(2):
            for l in range(2):
                if (k,l,i)==(1,1,1) or (l,i)==(0,0):
                    e=0
                else:
                    e=1
                if E[-1]!=e:
                    dp[i*2+j][k*2+l]=0
                if (l,i,j)==(1,1,1) or (i,j)==(0,0):
                    e=0
                else:
                    e=1
                if E[0]!=e:
                    dp[i*2+j][k*2+l]=0
ans=sum(dp[i][j] for i in range(4) for j in range(4))%mod
print(ans)