#include <iostream>
#include <cstdio>
#include <set>

using namespace std;

const int N = 2010;

char ch[N][N];
int h, w, k, ans;

int main() {
    scanf("%d%d%d", &h, &w, &k);
    for (int i = 1; i <= h; ++i) {
        string s;
        cin >> s;
        for (int j = 1; j <= w; ++j) {
            ch[i][j] = s[j - 1];
        }
    }

    for (int len = 1; len <= min(h, w); ++len) {
        for (int x1 = 1; x1 <= h - len; ++x1) {
            for (int y1 = 1; y1 <= w - len; ++y1) {
                set<char> s;
                for (int i = x1; i <= x1 + len; ++i) {
                    for (int j = y1; j <= y1 + len; ++j) {
                        s.insert(ch[i][j]);
                    }
                }
                if (s.size() == k) ++ans;
            }
        }
    }

    printf("%d\n", ans);

    return 0;
}