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#include <cstdio>
#include <vector>
using namespace std;

#define LLI long long int

struct Tree
{
    int N, sT;
    vector<int> D;

    int _get_sum(int to)
    {
        if (to == -1) return 0;
        return D[to + N - 1];
    }

    int sum(){ return _get_sum(sT - 1); }
    int get_min(int posL, int k)
    {
        int orig_posL = posL;
        posL += N-1;
        int posR = posL + k - 1;
        int result = min(D[posL], D[posR]);
        while (posL != posR)
        {
            if ((posL-1)/2 != (posR-1)/2){
                if (posL%2 == 1) result = min(result, D[posL+1]);
                if (posR%2 == 0) result = min(result, D[posR-1]);
            }
            posL = (posL-1)/2;
            posR = (posR-1)/2;
        }
        if (orig_posL == 0) return result;
        return result - _get_sum(orig_posL - 1);
    }

    int find_first_get_min(int posL, int L, int val)
    {
        val = val + _get_sum(posL - 1);
        int pos = posL + N - 1;
        int last_val = D[pos];

        if (D[pos] <= val) return 1;

        while ((pos%2==0) || (D[pos+1]>val)) pos = (pos-1)/2;
        pos += 1;
        if (D[pos] > val) printf("ERROR 1!\n");
        while (pos < N-1) pos = (D[2*pos+1] > val ? 2*pos+2 : 2*pos+1);

        return pos - posL + 1 - N + 1;
    }

    Tree(vector<char> &T){
        N = 1;
        sT = T.size();
        while(N < 2*T.size()) N=N*2;
        D.resize(N*2-1, 0);
        for(int i=0; i<T.size(); ++i) D[N-1+i] = T[i];
        for(int i=0; i<T.size(); ++i) D[N-1+i+T.size()] = T[i];
        for(int i=N; i<D.size(); ++i) D[i]+=D[i-1];
        for(int i=N-2; i>=0; --i) D[i] = min(D[2*i+1], D[2*i+2]);
    }
};

// ****************************************************************

int n, m;
vector<int> A;
char data[1000005];

int S, L;
vector<Tree> cycles;
vector<int> pos_in_cycle;

LLI get_time_after_child_loose(int k)
{
    LLI result = k + 1;

    Tree &T = cycles[k%S];
    int personal_min = T.get_min(pos_in_cycle[k], L);
    int global_sum = T.sum();

    if ((global_sum >= 0) && (A[k] + personal_min > 0)) return -1;
    if ((global_sum < 0) && (A[k] + personal_min > 0))
    {
        int full_cycles = (A[k] + personal_min) / (-global_sum);
        A[k] -= full_cycles * (-global_sum);

        if (A[k] + personal_min > 0)
        {
            full_cycles += 1;
            A[k] += global_sum;
        }

        LLI addon = full_cycles;
        addon = addon * (LLI)(L);
        addon = addon * (LLI)(n);
        result += addon;
    }

    LLI addon = T.find_first_get_min(pos_in_cycle[k], L, -A[k]) - 1;
    addon = addon * (LLI)(n);
    result += addon;
    return result;
}

// *************************************************************

int gcd(int a, int b){int c; while (b!=0){c = a%b; a=b; b=c; } return a; }
int main()
{
    // Wczytywanie danych
    scanf("%d", &n); A.resize(n);
    for(int i=0; i<n; ++i) scanf("%d", &A[i]);
    scanf("%d", &m);
    scanf("%s", data);

    // Obliczanie cykli i pozycji w cyklach
    S = gcd(n, m);
    L = m/S;
    pos_in_cycle.resize(n);
    vector<int> R(m);
    for(int i=0; i<S; ++i)
    {
        int val = i;
        vector<char> cycle(L);
        for(int j=0; j<L; ++j)
        {
            cycle[j] = (data[val] == 'W' ? 1 : -1);
            R[val] = j;
            val = (val+n)%m;
        }

        cycles.push_back(Tree(cycle));
    }
    for(int i=0; i<n; ++i) pos_in_cycle[i] = R[i%m];

    LLI result = -1;
    for(int k=0; k<n; ++k)
    {
        LLI time_to_loose = get_time_after_child_loose(k);
        if (time_to_loose == -1) continue;
        if ((time_to_loose < result) || (result == -1)) result = time_to_loose;
    }

    printf("%lld\n", result);
    return 0;
}