#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
int read()
{int x=0,f=1;char c=getchar();while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar();return x*f;
}
#define N 1000010
#define P 1000000007
int n,m,a[N],pre[N][2],p[2],f[N][3][2],delta[3][2];
void inc(int &x,int y){x+=y;if (x>=P) x-=P;}
int main()
{
#ifndef ONLINE_JUDGEfreopen("bzoj2958.in","r",stdin);freopen("bzoj2958.out","w",stdout);const char LL[]="%I64d\n";
#elseconst char LL[]="%lld\n";
#endifn=read(),m=read();char c=getchar();while (c<'A'||c>'Z') c=getchar();for (int i=1;i<=n;i++){a[i]=(c=='X')?2:(c=='B'?0:1);if (a[i]<2) p[a[i]]=i;pre[i][0]=p[0];pre[i][1]=p[1];c=getchar();}a[0]=2;f[0][0][0]=f[0][0][1]=1;delta[0][0]=(a[1]!=1),delta[0][1]=(a[1]!=0);for (int i=1;i<=n;i++){f[i][0][0]=delta[0][0],f[i][1][0]=delta[1][0],f[i][2][0]=delta[2][0];f[i][0][1]=delta[0][1],f[i][1][1]=delta[1][1],f[i][2][1]=delta[2][1];inc(delta[0][0],f[i][0][1]);inc(delta[1][0],f[i][1][1]);inc(delta[2][0],f[i][2][1]);inc(delta[0][1],f[i][0][0]);inc(delta[1][1],f[i][1][0]);inc(delta[2][1],f[i][2][0]);if (pre[i+1][1]<i-m+2){inc(delta[0][0],(P-f[i-m+1][0][1])%P);inc(delta[1][0],f[i-m+1][0][1]);}if (pre[i+1][0]<i-m+2){inc(delta[1][1],(P-f[i-m+1][1][0])%P);inc(delta[2][1],f[i-m+1][1][0]);}if (a[i+1]==0) delta[0][1]=delta[1][1]=delta[2][1]=0;if (a[i+1]==1) delta[0][0]=delta[1][0]=delta[2][0]=0;}cout<<(f[n][2][0]+f[n][2][1])%P;return 0;
}