#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#define pb push_back
#define inf 0x3f3f3f3f
using namespace std;
namespace INPUT{
    char buf[1<<20],*p1,*p2;
    #define gc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<20,stdin),p1==p2)?EOF:*p1++)
}
using namespace INPUT;
template<typename T>
inline T read(){
    T x=0,p=1;
    char ch=gc();
    for(;ch<'0'||ch>'9';ch=gc())
        if(ch=='-') p=-1;
    for(;ch>='0'&&ch<='9';ch=gc())
        x=(x<<3)+(x<<1)+(ch^48);
    return x*p;
}
const int N=55,M=N*3;
struct Edge{
    int u,v;
    int cap,flow;
    Edge(int u,int v,int cap,int flow):
        u(u),v(v),cap(cap),flow(flow){};
};
vector<Edge>edges;
vector<int>G[M];
void AddEdge(int u,int v,int cap){
    edges.pb(Edge(u,v,cap,0));
    edges.pb(Edge(v,u,0,0));
    int m=edges.size();
    G[u].pb(m-2),G[v].pb(m-1);
}
bool vis[M];
int d[M];
int src,des;
bool BFS(){
    queue<int>q;
    memset(vis,0,sizeof(vis));
    memset(d,inf,sizeof(d));
    q.push(src),d[src]=0,vis[src]=true;
    while(!q.empty()){
        int u=q.front();
        q.pop();
        for(auto i:G[u]){
            Edge& ed=edges[i];
            if(!vis[ed.v]&&ed.cap>ed.flow){
                d[ed.v]=d[u]+1;
                q.push(ed.v),vis[ed.v]=true;
            }
        }
    }
    return vis[des];
}
int cur[M];
int dinic(int u,int a){
    if(u==des||a==0) return a;
    int flow=0,f;
    for(int& i=cur[u];i<G[u].size();i++){
        int x=G[u][i];
        Edge& ed=edges[x];
        if(d[ed.v]==d[u]+1&&(f=dinic(ed.v,min(a,ed.cap-ed.flow)))>0){
            edges[x].flow+=f,edges[x^1].flow-=f;
            flow+=f,a-=f;
            if(!a) break;
        }
    }
    return flow;
}
int Maxflow(){
    int flow=0;
    while(BFS()){
        memset(cur,0,sizeof(cur));
        flow+=dinic(src,inf);
    }
    return flow;
}
int n,k;
int main(){
    freopen("P3153.in","r",stdin);
    freopen("P3153.out","w",stdout);
    n=read<int>(),k=read<int>();
    //boys:n(fav) n(unfav) girls:n des
    src=0,des=3*n+1;
    for(int i=1;i<=n;i++) AddEdge(src,i,0),AddEdge(i,n+i,k),AddEdge(n*2+i,des,0);
    char ch='?';
    for(int i=1;i<=n;i++){
        while(ch!='Y'&&ch!='N') ch=gc();
        for(int j=1;j<=n;j++) {
            if(ch=='Y') AddEdge(i,n*2+j,1);
            else AddEdge(n+i,n*2+j,1);
            ch=gc();
        }
    }
    int c=0,flow;
    do{
        for(auto i:G[src]) edges[i].cap++;
        for(auto i:G[des]) edges[i^1].cap++;
        flow=Maxflow();
    }while(flow==n&&++c);
    cout<<c<<endl;
}