#pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; typedef long long ll; typedef pair P; typedef bitset<16> BS; struct edge { int to, cost, id; }; const ll MOD = 1E+09 + 7; // =998244353; const ll INF = 1E18; const int MAX_N = 2E+05; ll dx[4] = { -1, 1, 0, 0 }, dy[4] = { 0, 0, -1, 1 }; ll dp1[MAX_N + 1][26], dp2[MAX_N + 1][26]; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); string s; cin >> s; int ns = s.size(); for (int i = 1; i <= ns; i++) { for (int j = 0; j < 26; j++) { dp1[i][j] = dp1[i - 1][j]; if (s[i - 1] - 'a' == j) { for (int a = 0; a < 26; a++) { dp1[i][j] += dp1[i - 1][a]; dp1[i][j] %= MOD; } dp1[i][j]++; } } } for (int i = 1; i <= ns; i++) { for (int j = 0; j < 26; j++) { dp2[i][j] = dp2[i - 1][j]; if (s[i - 1] - 'a' == j) { for (int a = 0; a < 26; a++) { if (a != j) { dp2[i][j] += dp2[i - 1][a] + dp1[i - 1][a]; } else { dp2[i][j] += dp2[i - 1][j]; } dp2[i][j] %= MOD; } dp2[i][j]++; } } } // for (int i = 1; i <= ns; i++) { // for (int j = 0; j < 26; j++) { // cout << "i = " << i << ", j = " << j << ", dp1 = " << dp1[i][j] << "\n"; // } // } // for (int i = 1; i <= ns; i++) { // for (int j = 0; j < 26; j++) { // cout << "i = " << i << ", j = " << j << ", dp2 = " << dp2[i][j] << "\n"; // } // } ll ans = 0; for (int a = 0; a < 26; a++) { ans += dp2[ns][a]; ans %= MOD; } cout << ans << "\n"; return 0; }