Buggy python submission (verdict: Runtime Error):
def main():
    n , m = map(int, input().split())
    con = list(set([tuple(map(int, input().split())) for i in range(m)]))
    if (len(con) > n) or (n != 1 and con[0] == (1,0)):
        print(-1)
        return
    ans = 10**(n-1)
    if (m == 0):
        print(ans)
        return
    tmp = -1
    for s,c in con:
        if (s == tmp):
            print(-1)
            return
        else:
            tmp = s
        if (s==1):
            ans += (c-1)*10**(n-1)
        else:
            ans += c*10**(n-s)
    print(ans)
main()    

Fixed submission:
def main():
    n , m = map(int, input().split())
    con = list(set([tuple(map(int, input().split())) for i in range(m)]))
    if (len(con) > n) or (m != 0 and n != 1 and con[0] == (1,0)):
        print(-1)
        return
    if (n == 1 and m == 0):
        print(0)
        return
    ans = 10**(n-1)
    if (m == 0):
        print(ans)
        return
    tmp = -1
    for s,c in con:
        if (s == tmp):
            print(-1)
            return
        else:
            tmp = s
        if (s==1):
            ans += (c-1)*10**(n-1)
        else:
            ans += c*10**(n-s)
    print(ans)
main()

Buggy python submission (verdict: Runtime Error):
def main():
    n , m = map(int, input().split())
    con = list(set([tuple(map(int, input().split())) for i in range(m)]))
    if (len(con) > n) or (n != 1 and con[0] == (1,0)):
        print(-1)
        return
    ans = 10**(n-1)
    tmp = -1
    for s,c in con:
        if (s == tmp):
            print(-1)
            return
        else:
            tmp = s
        if (s==1):
            ans += (c-1)*10**(n-1)
        else:
            ans += c*10**(n-s)
    print(ans)
main()   

Fixed submission:
def main():
    n , m = map(int, input().split())
    con = list(set([tuple(map(int, input().split())) for i in range(m)]))
    if (len(con) > n) or (m != 0 and n != 1 and con[0] == (1,0)):
        print(-1)
        return
    if (n == 1 and m == 0):
        print(0)
        return
    ans = 10**(n-1)
    if (m == 0):
        print(ans)
        return
    tmp = -1
    for s,c in con:
        if (s == tmp):
            print(-1)
            return
        else:
            tmp = s
        if (s==1):
            ans += (c-1)*10**(n-1)
        else:
            ans += c*10**(n-s)
    print(ans)
main()

Buggy python submission (verdict: Runtime Error):
def main():
    n , m = map(int, input().split())
    con = list(set([tuple(map(int, input().split())) for i in range(m)]))
    if (len(con) > n) or (con[0] == (1,0)):
        print(-1)
        return
    ans = 10**(n-1)
    tmp = -1
    for s,c in con:
        if (s == tmp):
            print(-1)
            return
        else:
            tmp = s
        if (s==1):
            ans += (c-1)*10**(n-1)
        else:
            ans += c*10**(n-s)
    print(ans)
main()    

Fixed submission:
def main():
    n , m = map(int, input().split())
    con = list(set([tuple(map(int, input().split())) for i in range(m)]))
    if (len(con) > n) or (m != 0 and n != 1 and con[0] == (1,0)):
        print(-1)
        return
    if (n == 1 and m == 0):
        print(0)
        return
    ans = 10**(n-1)
    if (m == 0):
        print(ans)
        return
    tmp = -1
    for s,c in con:
        if (s == tmp):
            print(-1)
            return
        else:
            tmp = s
        if (s==1):
            ans += (c-1)*10**(n-1)
        else:
            ans += c*10**(n-s)
    print(ans)
main()