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int solve(string s){
long long answer = 0;
map<int, int> m;
m[0] = 1;
int x = 0;
for (auto& c : s) {
int d = c - 'a';
x ^= 1 << d;
answer += m[x];
for (int i = 0; i < 26; ++i) {
answer += m[x ^ (1 << i)];
}
m[x] += 1;
}
return answer;
}