#include <bits/stdc++.h> 
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define int 	     	  long long   // [9,223,372,036,854,775,807 to -9.....808] 19 digits
#define pb                push_back 
#define all(x)            (x).begin(),(x).end()
#define mp                make_pair
#define vi                vector<int> 
#define vpi               vector<pair<int,int>>
#define mii               map<int,int>
#define x                 first
#define y                 second 
#define mem(a,x)          memset(a,x,sizeof(a))
#define rep(i,a,b)        for(int i=a;i<b;i++)
#define sz(x)             (int)((x).size())

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;

//const int32_t MOD=163577857; const int32_t hellhsh = 444440583533; const double pi=2*acos(0.0); const int32_t MOD=998244353; 
const int32_t MOD = 1e9+7;
const int32_t maxn=2e6+5;

struct mod_int {
	int32_t val;
	mod_int(long long v = 0) {if (v < 0) v = v % MOD + MOD; if (v >= MOD) v %= MOD; val = v; }
 
	static int32_t mod_inv(int32_t a, int32_t m = MOD) {
		int32_t g = m, r = a, x = 0, y = 1;
		while (r != 0) {
			int32_t q = g / r;
			g %= r; swap(g, r);
			x -= q * y; swap(x, y);
		}
		return x < 0 ? x + m : x;
	}
	static unsigned fast_mod(uint64_t x, unsigned m = MOD) {
		#if !defined(_WIN32) || defined(_WIN64)
		return x % m;
		#endif
		unsigned x_high = x >> 32, x_low = (unsigned) x;
		unsigned quot, rem;
		asm("divl %4\n"
			: "=a" (quot), "=d" (rem)
			: "d" (x_high), "a" (x_low), "r" (m));
		return rem;
	}
 
	explicit operator int() const {return val; }
	mod_int& operator+=(const mod_int &other) {val += other.val; if (val >= MOD) val -= MOD; return *this; }
	mod_int& operator-=(const mod_int &other) {val -= other.val; if (val < 0) val += MOD; return *this; }
	mod_int& operator*=(const mod_int &other) {val = fast_mod((uint64_t) val * other.val); return *this; }
	mod_int& operator/=(const mod_int &other) {return *this *= other.inv(); }
	friend mod_int operator+(const mod_int &a, const mod_int &b) { return mod_int(a) += b; }
	friend mod_int operator-(const mod_int &a, const mod_int &b) { return mod_int(a) -= b; }
	friend mod_int operator*(const mod_int &a, const mod_int &b) { return mod_int(a) *= b; }
	friend mod_int operator/(const mod_int &a, const mod_int &b) { return mod_int(a) /= b; }
	mod_int& operator++() {val = val == MOD - 1 ? 0 : val + 1; return *this; }
	mod_int& operator--() {val = val == 0 ? MOD - 1 : val - 1; return *this; }
	mod_int operator++(int32_t) { mod_int before = *this; ++*this; return before; }
	mod_int operator--(int32_t) { mod_int before = *this; --*this; return before; }
	mod_int operator-() const {return val == 0 ? 0 : MOD - val; }
	bool operator==(const mod_int &other) const { return val == other.val; }
	bool operator!=(const mod_int &other) const { return val != other.val; }
	mod_int inv() const {return mod_inv(val); }
	friend ostream& operator<<(ostream &stream, const mod_int &m) {return stream << m.val; }
	friend istream& operator>>(istream &stream, mod_int &m) {return stream >> m.val; }
 
	mod_int pow(long long p) const { //dont put a negetive p
		assert(p >= 0);
		mod_int a = *this, result = 1;
		while (p > 0) {
			if (p & 1)
				result *= a;
			
			a *= a;
			p >>= 1;
		}
		return result;
	}
};
mod_int fact[maxn];bool fbb=0;
void build(){fbb=1;fact[0]=1;rep(i,1,maxn)fact[i]=i*fact[i-1];}
mod_int C(int n,int r){if(fbb)return (fact[n]/(fact[r]*fact[n-r]));mod_int a=1,b=1;rep(i,0,r){a*=n-i;b*=i+1;}return a/b;}

void solve(){
    int k,n;string s;cin>>k>>s;
    n=sz(s);
    build();
    mod_int ans=mod_int(26).pow(n+k);
    rep(i,0,n){
        ans-=mod_int(25).pow(n+k-i)*C(n+k,i);
    }
    cout<<ans;
}

signed main() {
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int tc=1,k=1;                                                                                                                  
    //cin>>tc;
    while(tc--){
        //cout<<"Case #"<<k++<<": ";
        solve();
    }
    return 0;
}



Measured memory_bytes: 12068