http://codeforces.com/problemset/problem/520/C

题解：思维+数学+快速幂

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans,cnt,flag,temp,sum;
char str[N];
int a[5];
struct node{};
ll POW(ll a,ll b=MOD-2,ll c=MOD){
    ll res=1;
    ll base=a%c;
    while(b){
        if(b&1)res=(res*base)%c;
        base=(base*base)%c;
        b>>=1;
    }
    return res;
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    scanf("%d",&n);
    scanf("%s",str);
    for(int i=0;i<n;i++){
        if(str[i]=='A')a[0]++;
        if(str[i]=='C')a[1]++;
        if(str[i]=='G')a[2]++;
        if(str[i]=='T')a[3]++;
    }
    sort(a,a+4);
    for(int i=0;i<4;i++){
        if(a[i]==a[3])cnt++;
    }
    cout<<POW(cnt,n)<<endl;
    //}

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}