// 愚直解

#include <stdio.h>
#include <stdlib.h>
#define rep(i, l, r) for(int i = (l); i < (r); ++i)
#define MAX_N 200000
#define MAX_K 8
#define MAX_DIFF 33

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma warning(disable: 4996)

typedef struct _cell {
	int value;
	struct _cell* next;
	struct _cell* prev;
}CELL;

CELL* head[MAX_DIFF] = { NULL };

inline void insert_cell(int d, int v) {
	CELL* new_cell = (CELL*)malloc(sizeof(CELL));
	new_cell->value = v;
	new_cell->next = head[d];
	new_cell->prev = NULL;
	head[d] = new_cell;
	if (head[d]->next != NULL) {
		head[d]->next->prev = head[d];
	}
}

inline CELL* delete_cell(int d, CELL* p) {
	if (p == NULL) {
		return NULL;
	}
	CELL* pp = p->prev;
	if (pp != NULL) {
		pp->next = p->next;
	}
	else {
		head[d] = p->next;
	}
	CELL* np = p->next;
	if (np != NULL) {
		np->prev = p->prev;
	}
	free(p);
	return np;
}


int main(void) {
	int N, K;	scanf("%d", &N);	scanf("%d", &K);
	char s[MAX_N][MAX_K + 1];
	rep(i, 0, N) {
		scanf("%s", s[i]);
	}

	rep(i, 0, N) {
		int diff = 0;
		rep(j, 0, K) {
			int d = abs(s[i][j] - '0');
			diff += d;
			if (d > s[i][K]) {
				s[i][K] = d;
			}
		}
		insert_cell(diff, i);
	}

	int ans = 0;
	for (int i = MAX_DIFF - 1; i > 0; --i) {
		CELL* p1 = head[i];
		while (p1 != NULL) {
			rep(j, 0, i) {
				CELL* p2 = head[j];
				while (p2 != NULL) {
					if (s[p1->value][K] < s[p2->value][K]) {
						p2 = p2->next;
						continue;
					}
					int flag = 1;
					rep(k, 0, K) {
						if (s[p1->value][k] >= s[p2->value][k]) {
							continue;
						}
						flag = 0;
						break;
					}
					if (flag) {
						++ans;
						p2 = delete_cell(j, p2);
					}
					else {
						p2 = p2->next;
					}
				}
			}
			p1 = p1->next;
		}
	}
	printf("%d\n", ans);

	return 0;
}