Buggy python submission (verdict: Runtime Error):
n,m=[int(i) for i in input().split()]
badone=[int(input()) for i in range(m)]
badstares=[1 for i in range(n)]
for i in badone:
    badstares[i-1]=0


stares=[-1 for i in range(n)]
for i in range(n):
    
    i=n-1-i
    if i==n-1:
        stares[i]=1
    elif i==n-2:
        if badstares[i]==0:
            stares[i]=-1
        else:
            stares[i]=1
    else:
        if badstares[i]==0:
            stares[i]=-1
        else:
            if stares[i+1]==-1 and stares[i+2]==-1:
                    stares[i]=-1
            elif stares[i+1]==-1 and stares[i+2]!=-1:
                    stares[i]=stares[i+2]
            elif stares[i+2]==-1:
                stares[i]=stares[i+1]
            else:
                stares[i]=stares[i+1]+stares[i+2]
    
if stares[0]==-1 and stares[1]==-1:
    print(0)
elif stares[0]==-1:
    print(stares[1]%1000000007)
elif stares[1]==-1:
    print(stares[0]%1000000007)
else:
    print((stares[0]+stares[1])%1000000007)

Fixed submission:
n,m=[int(i) for i in input().split()]
badone=[int(input()) for i in range(m)]
badstares=[1 for i in range(n)]
for i in badone:
    badstares[i-1]=0


stares=[-1 for i in range(n)]
if n==1:
    print(1)
else:
    for i in range(n):

        i=n-1-i
        if i==n-1:
            stares[i]=1
        elif i==n-2:
            if badstares[i]==0:
                stares[i]=-1
            else:
                stares[i]=1
        else:
            if badstares[i]==0:
                stares[i]=-1
            else:
                if stares[i+1]==-1 and stares[i+2]==-1:
                        stares[i]=-1
                elif stares[i+1]==-1 and stares[i+2]!=-1:
                        stares[i]=stares[i+2]
                elif stares[i+2]==-1:
                    stares[i]=stares[i+1]
                else:
                    stares[i]=stares[i+1]+stares[i+2]

    if stares[0]==-1 and stares[1]==-1:
        print(0)
    elif stares[0]==-1:
        print(stares[1]%1000000007)
    elif stares[1]==-1:
        print(stares[0]%1000000007)
    else:
        print((stares[0]+stares[1])%1000000007)

Buggy python submission (verdict: Runtime Error):
n,m=[int(i) for i in input().split()]
badone=[int(input()) for i in range(m)]
badstares=[1 for i in range(n)]
for i in badone:
    badstares[i-1]=0


stares=[-1 for i in range(n)]
for i in range(n):
    
    i=n-1-i
    if i==n-1:
        stares[i]=1
    elif i==n-2:
        if badstares[i]==0:
            stares[i]=-1
        else:
            stares[i]=1
    else:
        if badstares[i]==0:
            stares[i]=-1
        else:
            if stares[i+1]==-1:
                if stares[i+2]==-1:
                    stares[i]=-1
                else:
                    stares[i]=stares[i+2]
            elif stares[i+2]==-1:
                stares[i]=stares[i+1]
            else:
                stares[i]=stares[i+1]+stares[i+2]
    
print(max(stares[0]+stares[1],0)%1000000007)


Fixed submission:
n,m=[int(i) for i in input().split()]
badone=[int(input()) for i in range(m)]
badstares=[1 for i in range(n)]
for i in badone:
    badstares[i-1]=0


stares=[-1 for i in range(n)]
if n==1:
    print(1)
else:
    for i in range(n):

        i=n-1-i
        if i==n-1:
            stares[i]=1
        elif i==n-2:
            if badstares[i]==0:
                stares[i]=-1
            else:
                stares[i]=1
        else:
            if badstares[i]==0:
                stares[i]=-1
            else:
                if stares[i+1]==-1 and stares[i+2]==-1:
                        stares[i]=-1
                elif stares[i+1]==-1 and stares[i+2]!=-1:
                        stares[i]=stares[i+2]
                elif stares[i+2]==-1:
                    stares[i]=stares[i+1]
                else:
                    stares[i]=stares[i+1]+stares[i+2]

    if stares[0]==-1 and stares[1]==-1:
        print(0)
    elif stares[0]==-1:
        print(stares[1]%1000000007)
    elif stares[1]==-1:
        print(stares[0]%1000000007)
    else:
        print((stares[0]+stares[1])%1000000007)