package contest190816; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; public class D2 { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(), m = ni(), K = ni(); char[][] map = nm(n, m); int I = 999999999; int[][][] all = new int[26][][]; for(int u = 0;u < 26;u++){ int[][] dp = new int[n+1][m+1]; for(int i = 0;i <= n;i++){ for(int j = 0;j <= m;j++){ if(i == n || j == m){ dp[i][j] = I; }else{ dp[i][j] = map[i][j]-'a' == u ? 0 : I; } } } for(int i = n-1;i >= 0;i--){ for(int j = m-1;j >= 0;j--){ int v = dp[i][j]; if(dp[i+1][j] + 1 < v)v = dp[i+1][j] + 1; if(dp[i][j+1] + 1 < v)v = dp[i][j+1] + 1; if(dp[i+1][j+1] + 1 < v)v = dp[i+1][j+1] + 1; dp[i][j] = v; } } all[u] = dp; } long ret = 0; int[] temp = new int[26]; for(int i = 0;i < n;i++){ for(int j = 0;j < m;j++){ for(int k = 0;k < 26;k++){ temp[k] = all[k][i][j]; } Arrays.sort(temp); int upper = temp[K]; int lower = temp[K-1]; upper = Math.min(upper, n-i); upper = Math.min(upper, m-j); ret += Math.max(0, upper-lower); } } out.println(ret); } void run() throws Exception { // int n = 2000, m = 99999; // Random gen = new Random(); // StringBuilder sb = new StringBuilder(); // sb.append(n + " "); // sb.append(n + " "); // sb.append(1 + " "); // for (int i = 0; i < n; i++) { // for(int j = 0;j < n;j++){ // sb.append("a"); // } // sb.append("\n"); // } // INPUT = sb.toString(); is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new D2().run(); } private byte[] inbuf = new byte[1024]; public int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }