#include <stdio.h>

#include <stdlib.h>

#include <stdbool.h>

#define MAXN 100000

char s[MAXN];

int dp[MAXN];

char pair[2];

bool invalid[26][26];

int max(int a, int b) { return a > b ? a : b; }

int main() {

int n, m;

scanf("%d", &n);

scanf("%s", s);

scanf("%d", &m);

int i, j;

for (i = 0; i < m; i++) {

scanf("%s", pair);

invalid[pair[0] - 'a'][pair[1] - 'a']

= invalid[pair[1] - 'a'][pair[0] - 'a'] = true;

}

//DP

bool invalid_ij;

int ans = 0;

for (i = 0; i < n; i++) {

dp[i] = 1;

for (j = i - 1; j >= 0; j--) {

invalid_ij = invalid[s[i] - 'a'][s[j] - 'a'];

if (s[i] != s[j]) {

if (invalid_ij) continue;

dp[i] = max(dp[i], dp[j] + 1);

}

else {

if (invalid_ij)

dp[i] = max(dp[i], dp[j]);

else

dp[i] = max(dp[i], dp[j] + 1);

break;

}

}

ans = max(ans, dp[i]);

}

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

exit(0);

}