#include<cstdio>

 #include<cstdlib>

 #include<cstring>

 #include<cmath>

 #include<algorithm>

 #define N 10005

 using namespace std;

 int  next[N];

 int n,m;

 char s1[N];//模板串

 char s2[N];//主串

 int len1,len2;

 int ans1,ans2;

 char str1[N][];

 void getnext(int plen){

     int i = ,j = -;

     next[]=-;

     while( i<plen ){

         if(j==-||s1[i]==s1[j]){

             ++i;++j;

          // if(s1[i]!=s1[j] )

             next[i] = j;

          // else

           //  next[i] = next[j];

         }

         else

             j = next[j];

     }

 }

 int gcd(int a, int  b){

     if(b==)

         return a;

     return gcd(b,a%b);

 }

 int lcm(int  a, int  b){//两个数的最小公倍数

    return a*b/gcd(a, b);

 }

 int main(){

    while(~scanf("%d%d",&n,&m)){

         ans1=;

         ans2=;

         int maxn=;

        for(int i=;i<=n;i++){

         scanf("%s",s1);

         strcpy(str1[i],s1);

         getnext(m);

        // printf("**%d\n",m-next[m]);

          maxn=max(maxn,m-next[m]);

        ans1=lcm(ans1,m-next[m]);

        }

        for(int i=;i<m;i++){

           for(int j=;j<=n;j++){

             s1[j-]=str1[j][i];

           }

              getnext(n);

          ans2=lcm(ans2,n-next[n]);

        }

        if(maxn*>=m)ans1=maxn;

        else if(ans1>m)ans1=m;

        if(ans2>n)ans2=n;

        printf("%d\n",ans1*ans2);

    }

 }