d=[set() for _ in range(26)]
        for idea in ideas:
            pre=ord(idea[0])-ord('a')
            suf=idea[1:]
            d[pre].add(suf)
        res=0
        for i in range(26):
            for j in range(26):
                if i!=j:
                    m=len(d[i].intersection(d[j]))
                    res+=(len(d[i])-m)*(len(d[j])-m)
        return res