#include<iostream>
#include<vector>
#include<string>
using namespace std;

long long N, p, n, k, val[27];

int main () {
    cin.tie(0);
    cout.tie(0);

    vector<int> kat;
    cin >> N;
    for(int i = 2; i <= N; i++)  {
        if(N % i == 0) {
            p = i; break;
        }
    }
    n = 0; long long xx = 1;
    while(xx < N) {
        n++;
        xx *= p;
    }

    int typ[N]; char cc; string ssss;

    vector<long long> znaki[n+2][29];// 28 to '?'
    for(int s = 0; s < 29; s++) {
        xx = N;
        for(int i = 0; i <= n; i ++) {
            znaki[i][s].resize(xx);
            xx /= p;
        }
    }

    int zap = '?' - 'A';
    cin>>ssss;
    for(int i = 0; i < N; i++) {
        typ[i] = (int) ssss[i];
        typ[i] -= 'A';
        for(int s = 0; s < 29;s ++) {
            znaki[0][s][i] = 0;
        }
        if(typ[i] == zap) {
            znaki[0][28][i] = 1;
        }
        else {
            znaki[0][typ[i]][i] = 1;
        }
    }

    cin >> k;

    for(int i = 0; i < k; i++) {
        cin >> cc;
        cin >> val[cc - 'A'];
        kat.push_back(cc - 'A');
    }
    long long maksi = 0;
    kat.push_back(28);

    for(int i = 0; i < k; i ++) {
        maksi = max(maksi, val[i]);
    }

    if(N == 1) {
        if(typ[0] == zap) {
            cout << maksi << '\n';
        }
        else {
            cout << val[typ[0]] << '\n';
        }

        return 0;
    }
    /// ZNAKI ////
    for(int s : kat) {
        xx = N/p;
        for(int i = 0; i < n; i ++) {// xx = p^(n-i-1)
            for(int x = 0; x < xx; x ++) {
                znaki[i + 1][s][x] = 0;
                for(int l = 0; l < p; l ++) {
                    znaki[i + 1][s][x] += znaki[i][s][x + l * xx];
                }
            }
            xx /= p;
        }
    }
    
    ///////////////////////////////////////

    vector<long long> DP[n+2];
    xx = N;
    for(int i = 0; i <= n; i ++) {
        DP[i].resize(xx);
        xx /= p;
    }

    for(int x = 0; x < N; x ++) {
        if(typ[x] == zap) {
            DP[0][x] = maksi;
        }
        else {
            DP[0][x] = val[typ[x]];
        }
    }
    xx = N/p; long long pi = p;
    for(int i = 0; i < n; i ++) {// xx = p^(n-i-1), pi = p ^ (i+1)
        for(int x = 0; x < xx; x ++) {
            DP[i + 1][x] = 0;
            for(int l = 0; l < p; l ++) {
                DP[i + 1][x] += DP[i][x + l * xx];
            }
            if(znaki[i + 1][28][x] == pi) {
                DP[i + 1][x] = max(DP[i+1][x], (i+2) * pi * maksi);
            }
            else {
                int ilez = 0;
                int ktore;
                for(int s : kat) {
                    if(znaki[i+1][s][x] > 0 && s < 28) {
                        ilez ++;
                        ktore = s;
                    }
                }
                if(ilez == 1) {
                    DP[i + 1][x] = max(DP[i+1][x], (i+2) * pi * val[ktore]);
                }
            }
                
        }
        xx /= p;
        pi *= p;
    }

    cout << DP[n][0] << '\n';
    

    return 0;
}