#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define all(a) a.begin(),a.end()
#define pb emplace_back
#define eb emplace_back
#define lb(v,k) (lower_bound(all(v),k)-v.begin())
#define ub(v,k) (upper_bound(all(v),k)-v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T,vector<T>,greater<T>>
#define dame(a) {out(a);return 0;}
#define decimal cout<<fixed<<setprecision(15);
#define dupli(a) a.erase(unique(all(a)),a.end())
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef tuple<ll,ll,ll,ll> PPP;
typedef multiset<ll> S;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vvvvi=vector<vvvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
using vvb=vector<vb>;
const ll inf=1001001001001001001;
const ll INF=1001001001;
const ll mod=1000000007;
const long double eps=1e-60;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())cout<<'('<<v[i].fi<<','<<v[i].se<<')';cout<<'\n';}
template<class T> void outvvp(T v){rep(i,v.size())outvp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size())outv(v[i]);}
template<class T> bool isin(T x,T l,T r){return (l)<=(x)&&(x)<=(r);}
template<class T> void yesno(T b){if(b)out("yes");else out("no");}
template<class T> void YesNo(T b){if(b)out("Yes");else out("No");}
template<class T> void YESNO(T b){if(b)out("YES");else out("NO");}
template<class T> void noyes(T b){if(b)out("no");else out("yes");}
template<class T> void NoYes(T b){if(b)out("No");else out("Yes");}
template<class T> void NOYES(T b){if(b)out("NO");else out("YES");}
void outs(ll a,ll b){if(a>=inf-100)out(b);else out(a);}
ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll modpow(ll a,ll b){a%=mod;if(b==0)return 1;if(b&1)return a*modpow(a,b-1)%mod;ll k=modpow(a,b/2);return k*k%mod;}

ll solve(ll n,ll k){
    //outp(P(n,k));
    chmin(k,n-1);
    vi dp(n+1);
    ll sum=1;
    dp[0]=1;
    REP(i,1,n+1){
        dp[i]=sum;
        sum=(sum+dp[i])%mod;
        if(i>k)sum=(sum-dp[i-k-1]+mod)%mod;
    }
    //outv(dp);
    ll res=0;
    REP(i,n-k,n+1)res=(res+dp[i-1]*(n-i+1))%mod;
    //rep(i,k+1)res=(res+dp[n-i-1]*(i+1))%mod;
    return res;
}

int main(){
    ll n,m;cin>>n>>m;
    string s;cin>>s;
    vi v(m);
    bool dif=false;
    rep(i,m){
        if(s[i]==s[0])v[i]=1;
        else dif=true;
    }
    if(!dif){
        out(solve(n,1));
    }
    else{
        if(n&1)dame(0);
        int w=0;
        while(w<m){
            if(!v[w])break;
            w++;
        }
        ll mi=w;
        w++;
        ll cnt=0;
        while(w<m){
            if(!v[w]){
                if(cnt&1)chmin(mi,cnt);
                cnt=0;
            }
            else cnt++;
            w++;
        }
        out(solve(n/2,mi/2)*2%mod);
    }
}

Measured memory_bytes: 3716