use std::cmp::*; // https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, chars) => { read_value!($next, String).chars().collect::>() }; ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } // Tags: log-factor-optimization fn main() { input! { h: usize, w: usize, k: usize, c: [chars; h], } let mut acc = vec![vec![[0; 26]; w + 1]; h + 1]; for u in 0..26 { for i in 0..h { for j in 0..w { acc[i + 1][j + 1][u] = acc[i + 1][j][u] + acc[i][j + 1][u] - acc[i][j][u] + if c[i][j] as u8 - b'a' == u as u8 { 1 } else { 0 }; } } } let kind = |i: usize, j: usize, x: usize| -> usize { let mut ans = 0; for u in 0..26 { if acc[i + x][j + x][u] - acc[i][j + x][u] - acc[i + x][j][u] + acc[i][j][u] > 0 { ans += 1; } } ans }; let mut tot = 0; for (is, js) in (0..h).map(|i| (i, 0)).chain((1..w).map(|j| (0, j))) { let mut lb = 0; let mut ub = 0; let lim = min(h - is, w - js); for i in 0..lim { lb = max(lb, i); ub = max(ub, i); while lb <= lim && kind(is + i, js + i, lb - i) < k { lb += 1; } while ub <= lim && kind(is + i, js + i, ub - i) <= k { ub += 1; } tot += (ub - lb) as i64; } } println!("{}", tot); }