fn getline() -> String { let mut ret = String::new(); std::io::stdin().read_line(&mut ret).ok().unwrap(); ret } // https://github.com/rust-lang-ja/ac-library-rs/blob/master/src/string.rs // Verified by: https://atcoder.jp/contests/abc213/submissions/25662432 fn sa_naive(s: &[T]) -> Vec { let n = s.len(); let mut sa: Vec = (0..n).collect(); sa.sort_by(|&(mut l), &(mut r)| { if l == r { return std::cmp::Ordering::Equal; } while l < n && r < n { if s[l] != s[r] { return s[l].cmp(&s[r]); } l += 1; r += 1; } if l == n { std::cmp::Ordering::Less } else { std::cmp::Ordering::Greater } }); sa } fn sa_doubling(s: &[i32]) -> Vec { let n = s.len(); let mut sa: Vec = (0..n).collect(); let mut rnk: Vec = s.to_vec(); let mut tmp = vec![0; n]; let mut k = 1; while k < n { let cmp = |&x: &usize, &y: &usize| { if rnk[x] != rnk[y] { return rnk[x].cmp(&rnk[y]); } let rx = if x + k < n { rnk[x + k] } else { -1 }; let ry = if y + k < n { rnk[y + k] } else { -1 }; rx.cmp(&ry) }; sa.sort_by(cmp); tmp[sa[0]] = 0; for i in 1..n { tmp[sa[i]] = tmp[sa[i - 1]] + if cmp(&sa[i - 1], &sa[i]) == std::cmp::Ordering::Less { 1 } else { 0 }; } std::mem::swap(&mut tmp, &mut rnk); k *= 2; } sa } trait Threshold { fn threshold_naive() -> usize; fn threshold_doubling() -> usize; } enum DefaultThreshold {} impl Threshold for DefaultThreshold { fn threshold_naive() -> usize { 10 } fn threshold_doubling() -> usize { 40 } } // |returned| = |s| // Complexity: O(|s| upper) #[allow(clippy::cognitive_complexity)] fn sa_is(s: &[usize], upper: usize) -> Vec { let n = s.len(); match n { 0 => return vec![], 1 => return vec![0], 2 => return if s[0] < s[1] { vec![0, 1] } else { vec![1, 0] }, _ => (), } if n < T::threshold_naive() { return sa_naive(s); } if n < T::threshold_doubling() { let s: Vec = s.iter().map(|&x| x as i32).collect(); return sa_doubling(&s); } let mut sa = vec![0; n]; let mut ls = vec![false; n]; for i in (0..n - 1).rev() { ls[i] = if s[i] == s[i + 1] { ls[i + 1] } else { s[i] < s[i + 1] }; } let mut sum_l = vec![0; upper + 1]; let mut sum_s = vec![0; upper + 1]; for i in 0..n { if !ls[i] { sum_s[s[i]] += 1; } else { sum_l[s[i] + 1] += 1; } } for i in 0..=upper { sum_s[i] += sum_l[i]; if i < upper { sum_l[i + 1] += sum_s[i]; } } // sa's origin is 1. let induce = |sa: &mut [usize], lms: &[usize]| { for elem in sa.iter_mut() { *elem = 0; } let mut buf = sum_s.clone(); for &d in lms { if d == n { continue; } let old = buf[s[d]]; buf[s[d]] += 1; sa[old] = d + 1; } buf.copy_from_slice(&sum_l); let old = buf[s[n - 1]]; buf[s[n - 1]] += 1; sa[old] = n; for i in 0..n { let v = sa[i]; if v >= 2 && !ls[v - 2] { let old = buf[s[v - 2]]; buf[s[v - 2]] += 1; sa[old] = v - 1; } } buf.copy_from_slice(&sum_l); for i in (0..n).rev() { let v = sa[i]; if v >= 2 && ls[v - 2] { buf[s[v - 2] + 1] -= 1; sa[buf[s[v - 2] + 1]] = v - 1; } } }; // origin: 1 let mut lms_map = vec![0; n + 1]; let mut m = 0; for i in 1..n { if !ls[i - 1] && ls[i] { lms_map[i] = m + 1; m += 1; } } let mut lms = Vec::with_capacity(m); for i in 1..n { if !ls[i - 1] && ls[i] { lms.push(i); } } assert_eq!(lms.len(), m); induce(&mut sa, &lms); if m > 0 { let mut sorted_lms = Vec::with_capacity(m); for &v in &sa { if lms_map[v - 1] != 0 { sorted_lms.push(v - 1); } } let mut rec_s = vec![0; m]; let mut rec_upper = 0; rec_s[lms_map[sorted_lms[0]] - 1] = 0; for i in 1..m { let mut l = sorted_lms[i - 1]; let mut r = sorted_lms[i]; let end_l = if lms_map[l] < m { lms[lms_map[l]] } else { n }; let end_r = if lms_map[r] < m { lms[lms_map[r]] } else { n }; let same = if end_l - l != end_r - r { false } else { while l < end_l { if s[l] != s[r] { break; } l += 1; r += 1; } l != n && s[l] == s[r] }; if !same { rec_upper += 1; } rec_s[lms_map[sorted_lms[i]] - 1] = rec_upper; } let rec_sa = sa_is::(&rec_s, rec_upper); for i in 0..m { sorted_lms[i] = lms[rec_sa[i]]; } induce(&mut sa, &mut sorted_lms); } for elem in sa.iter_mut() { *elem -= 1; } sa } fn suffix_array_lowercase(s: &[char]) -> Vec { let s: Vec = s.iter().map(|&x| (x as u8 - b'a') as usize).collect(); sa_is::(&s, 25) } // s.len() == sa.len() must hold. // Verified by: https://yukicoder.me/submissions/704334 struct LCP { inv_sa: Vec, spt: Vec> } impl LCP { pub fn new(s: &[T], sa: &[usize]) -> LCP { let n = sa.len(); assert_eq!(s.len(), n); let mut inv_sa = vec![0; n]; for i in 0..n { inv_sa[sa[i]] = i; } let lcp = Self::create_lcp(s, sa); let spt = Self::create_sparse_table(&lcp); LCP { inv_sa: inv_sa, spt: spt, } } fn create_lcp(s: &[T], sa: &[usize]) -> Vec { let n = s.len(); let mut rank = vec![0; n]; let mut lcp = vec![0; n - 1]; for i in 0..n { rank[sa[i]] = i; } let mut h: usize = 0; for i in 0..n { if rank[i] == 0 { continue; } let j = sa[rank[i] - 1]; h = h.saturating_sub(1); while j + h < n && i + h < n { if s[j + h] != s[i + h] { break; } h += 1; } lcp[rank[i] - 1] = h; } return lcp; } fn create_sparse_table(lcp: &[usize]) -> Vec> { let n = lcp.len(); let mut h: usize = 1; while (1 << h) <= n { h += 1; } let mut st: Vec> = vec![Vec::new(); h]; st[0] = Vec::from(lcp); for j in 1 .. h { st[j] = vec![0; n + 1 - (1 << j)]; for i in 0 .. n + 1 - (1 << j) { st[j][i] = std::cmp::min( st[j - 1][i], st[j - 1][i + 1_usize.wrapping_shl(j as u32 - 1)]); } } return st; } pub fn get_lcp(&self, f: usize, s: usize) -> usize { let n = self.inv_sa.len(); if f == n || s == n { return 0; } let f = self.inv_sa[f]; let s = self.inv_sa[s]; let (f, s) = if f > s { (s, f) } else { (f, s) }; assert!(f < s); let usize_size = usize::max_value().count_ones(); let diff = usize_size - 1 - (s - f).leading_zeros(); // topmost 1 return std::cmp::min(self.spt[diff as usize][f], self.spt[diff as usize][s - 1_usize.wrapping_shl(diff)]); } } fn main() { let s: Vec<_> = getline().trim().chars().collect(); let sa = suffix_array_lowercase(&s); let lcp = LCP::new(&s, &sa); let n = s.len(); let mut dp = vec![0; n / 2 + 1]; const MOD: i64 = 1_000_000_007; dp[0] = 1; for i in 1..n / 2 + 1 { for j in 0..i { if lcp.get_lcp(j, n - i) >= i - j { dp[i] = (dp[i] + dp[j]) % MOD; } } } let mut ans = 0; for i in 0..n / 2 + 1 { ans = (ans + dp[i]) % MOD; } println!("{}", ans); }