#include<stdio.h>
#define same 1000000001

int main(void) {
	int N, count = 0;
	int b;
	int hash[100][10001];
	int hashcount[100] = { 0 };
	int check;
	scanf("%d", &N);
	for (int i = 0; i < N; i++) {
		scanf("%d", &b);
		hash[b % 10][hashcount[b % 10]] = b;
		hashcount[b % 10]++;
	}
	for (int i = 0; i < 100; i++) {
		for (int j = 0; j<hashcount[i]; j++) {
			if (hash[i][j] == same) {
				continue;
			}
			check = 1;
			for (int k = j + 1; k <= hashcount[i]; k++) {
				if (hash[i][j] == hash[i][k]) {
					hash[i][k] = same;
					check = 0;
				}
			}
			if (check) {
				count++;
			}
		}
	}
	printf("%d", count);
}