// compile: make data
// run: ./data < data.in
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#ifdef LOCAL
#include <debug/codeforces.h>
#define debug(x...) _debug_print(#x, x);
#define Debug(x...) _debug_print_format(#x, x);
std::ifstream terminal("/dev/tty");
#define PP cerr<<"\033[1;30mpause...\e[0m",terminal.ignore();
#else
#define debug(x...)
#define Debug(x...)
#define PP
#endif
template<typename...Args> void print_(Args...args){((cout<<args<<" "),...)<<endl;}
#define VI vector<int>
#define VII vector<vector<int>>
#define VIII vector<vector<vector<int>>>
#define rep(i,a,b) for(int i=(a);i<(int)(b);++i)
#define sz(v) ((int)(v).size())
#define print(...) print_(__VA_ARGS__);
#define FIND(a, x) ((find(a.begin(),a.end(),(x))!=a.end())?1:0)
#define cmin(x,...) x=min({(x), __VA_ARGS__})
#define cmax(x,...) x=max({(x), __VA_ARGS__})
#define INTMAX (int)(9223372036854775807)
#define INF (int)(1152921504606846976)
#define NaN (int)(0x8b88e1d0595d51d1)
#define double long double
#define int long long
#define uint unsigned int
#define MAXN 200010
#define P 1000000007
#define MOD0 11635419037240549
#define MOD1 10487639585196761
#define MOD2 10671969493879289

namespace math {
    constexpr int safe_mod(int x, int m) {
        x %= m;
        if (x < 0) x += m;
        return x;
    }
    struct barrett {
        uint _m, im;
        explicit barrett(uint m) : _m(m), im((uint)(-1) / m + 1) {}
        uint umod() const { return _m; }
        uint mul(unsigned int a, unsigned int b) const {
            uint z = a;
            z *= b;
            uint x = (uint)(((unsigned __int128)(z)*im) >> 64);
            uint y = x * _m;
            return (uint)(z - y + (z < y ? _m : 0));
        }
    };
    int pow_mod(int x, int n, int m = INF) {
        if (m == 1) return 0;
        barrett bt((uint)(m));
        uint r = 1, y = (uint)(safe_mod(x, m));
        while (n) {
            if (n & 1) r = bt.mul(r, y);
            y = bt.mul(y, y);
            n >>= 1;
        }
        return r;
    }
}

template <char F, int B, int N> struct strhash {
    const int M[10] = {999999937, 999999929, 999999893, 999999883, 999999797, 999999761, 999999757, 999999739, 999999733, 999999677};
    string s;
    int len;
    vector<vector<int>> pw, hs;
    strhash(string S): s(S), len(S.size()) {
        assert(N <= 10);
        pw.assign(len, vector<int>(N));
        fill(pw[0].begin(), pw[0].end(), 1);
        rep(i, 1, len) rep(j, 0, N) pw[i][j] = pw[i-1][j] * B % M[j];
        hs.assign(len+1, vector<int>(N, 0));
        rep(i, 0, len) rep(j, 0, N) hs[i+1][j] = (hs[i][j] * B + s[i] - F) % M[j];
    }
    vector<int> hash(int l, int r) {
        if (!l) return hs[r+1];
        vector<int> res(N);
        rep(i, 0, N) res[i] = (hs[r+1][i] - hs[l][i] * pw[r-l+1][i] % M[i] + M[i]) % M[i];
        return res;
    }
};

// 11813125
int32_t main() {
    ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);

    int n; cin >> n;
    string s; cin >> s;
    int m = s.length();

    strhash<'A', 26, 2> hs(s);
    auto getlen = [&](int len, char c) -> int {
        string cur = s.substr(0, len) + c;
        int maxlen = cur.length();
        strhash<'A', 26, 2> hcur(cur);
        while (cur.substr(cur.length() - maxlen, maxlen) != s.substr(0, maxlen)) --maxlen;
        return maxlen;
    };
    vector<vector<int>> nxt(m+1, vector<int>(26, 0));
    rep(i, 0, m+1) rep(c, 0, 26) nxt[i][c] = getlen(i, (char)(c + 'A'));

    vector<vector<int>> dp(n+1, vector<int>(m+1, 0));
    dp[0][0] = 1;
    rep(i, 0, n) {
        rep(j, 0, min(i+1, m)) {
            rep(c, 0, 26) {
                int len = nxt[j][c];
                dp[i+1][len] += dp[i][j];
                dp[i+1][len] %= P;
            }
        }
    }
    int sum = math::pow_mod(26, n, P), ans = 0;
    rep(i, 0, m) ans = (ans + dp[n][i]) % P;
    ans = (sum - ans + P) % P;
    cout << ans << endl;

    return 0;
}