#define IOS ios_base::sync_with_stdio(0); cin.tie(0);

 #include <cstdio>//sprintf islower isupper

 #include <cstdlib>//malloc  exit strcat itoa system("cls")

 #include <iostream>//pair

 #include <fstream>//freopen("C:\\Users\\13606\\Desktop\\草稿.txt","r",stdin);

 #include <bitset>

 //#include <map>

 //#include<unordered_map>   https://www.nitacm.com/problem_show.php?pid=585

 #include <vector>

 #include <stack>

 #include <set>

 #include <string.h>//strstr substr

 #include <string>

 #include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;

 #include <cmath>

 #include <deque>

 #include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less

 #include <vector>//emplace_back

 //#include <math.h>

 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor

 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)

 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation

 #define fo(a,b,c) for(register int a=b;a<=c;++a)

 #define fr(a,b,c) for(register int a=b;a>=c;--a)

 #define mem(a,b) memset(a,b,sizeof(a))

 #define pr printf

 #define sc scanf

 #define ls rt<<1

 #define rs rt<<1|1

 typedef long long ll;

 #define rint register int

 void swapp(int &a,int &b);

 double fabss(double a);

 int maxx(int a,int b);

 int minn(int a,int b);

 int Del_bit_1(int n);

 int lowbit(int n);

 int abss(int a);

 //const long long INF=(1LL<<60);

 const double E=2.718281828;

 const double PI=acos(-1.0);

 const int inf=(<<);

 const double ESP=1e-;

 const int mod=(int)1e9+;

 const int N=(int)2e6+;

 void PR(int _[],int n)

 {

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

         pr("%d ",_[i]);

     pr("\n");

 }

 char s[N],s1[N],s2[N];

 int a[N];

 int sa[N],rk[N],s_a[N],t[N];//桶的大小要为N,因为放的是rank;

 int height[N],h[N];//h是位置i的长度,heidgt是ranki的长度;

 void Init(int _[],int n)

 {

     for(rint i=;i<=n;++i)

         _[i]=;

 }

 bool cmp(int i,int j,int k)

 {

     return s_a[i]==s_a[j]&&s_a[i+k]==s_a[j+k];

 }

 void Sort(int len)

 {

     int m=;//字符集大小;

     for(rint i=;i<=len;++i) ++t[a[i]],rk[i]=a[i];

     for(rint i=;i<=m;++i) t[i]+=t[i-];

     for(rint i=len;i>=;--i) sa[t[rk[i]]--]=i;

     for(rint k=;k<=len;k<<=)

     {

         int cnt=;

         //按第二个rank排;

         for(rint i=len-k+;i<=len;++i) s_a[++cnt]=i;

         for(rint i=;i<=len;++i)if(sa[i]>k) s_a[++cnt]=sa[i]-k;

         //按第一个rank排;

         Init(t,m);

         for(rint i=;i<=len;++i) ++t[rk[s_a[i]]];

         for(rint i=;i<=m;++i) t[i]+=t[i-];

         for(rint i=len;i>=;--i) sa[t[rk[s_a[i]]]--]=s_a[i];

         swap(rk,s_a);rk[sa[]]=cnt=;

         for(rint i=;i<=len;++i)

             rk[sa[i]]=cmp(sa[i],sa[i-],k)?cnt:++cnt;

         if(cnt==len)break;

         m=cnt;

     }

     //求height数组;

     for(rint i=;i<=len;++i)

     {

         h[i]=max(,h[i-]-);

         if(rk[i]==)continue;

         while(a[i+h[i]]==a[sa[rk[i]-]+h[i]]) ++h[i];

     }

     for(rint i=;i<=len;++i) height[i]=h[sa[i]];

 }

 int ans[N],res[N];

 int main()

 {

 //    freopen("D:\\Chrome Download\\testdata (2).in","r",stdin);

     int len1,len2;

     sc("%d%d",&len1,&len2);

     sc("%s%s",s1+,s2+);

     int len=;

     for(int i=len1;i>=;--i)

         a[++len]=s1[i]-'a'+;

     a[++len]=;

     for(int i=len2;i>=;--i)

         a[++len]=s2[i]-'a'+;

     Sort(len);

 //    PR(height,len);

 //    PR(sa,len);

 //    PR(rk,len);

     int temp=;

     for(int i=;i<=len;++i)

     {

     //    temp=min(temp,height[i+1]);

         if(sa[i]<=len1)

             temp=height[i+];

         else

             ans[i]=temp,temp=min(temp,height[i+]);

     }

     temp=;

     for(int i=len;i>=;--i)

     {

     //    temp=min(temp,height[i+1]);

         if(sa[i]<=len1)

             temp=height[i];

         else

             ans[i]=max(ans[i],temp),temp=min(temp,height[i]);

     }

 //    PR(ans,len);

     ll Ans=;

     for(int i=len;i>=len1+;--i)

     {

         res[i]=max(res[i+],ans[rk[i]]);

         Ans+=res[i];

     }

     pr("%lld\n",Ans);

     return ;

 }

 /**************************************************************************************/

 int maxx(int a,int b)

 {

     return a>b?a:b;

 }

 void swapp(int &a,int &b)

 {

     a^=b^=a^=b;

 }

 int lowbit(int n)

 {

     return n&(-n);

 }

 int Del_bit_1(int n)

 {

     return n&(n-);

 }

 int abss(int a)

 {

     return a>?a:-a;

 }

 double fabss(double a)

 {

     return a>?a:-a;

 }

 int minn(int a,int b)

 {

     return a<b?a:b;

 }