#include<stdio.h>
#include<algorithm>
const int N=100005;

#define ull long long
const ull B=233,P=1226999999;

int n,ans;
ull h1[2][N],h2[2][N],pw[N];
char s[2][N];

inline ull H1(int f,int l,int r){
    return (h1[f][r]+P-h1[f][l-1]*pw[r-l+1]%P)%P;
}

inline ull H2(int f,int l,int r){
    return (h2[f][l]+P-h2[f][r+1]*pw[r-l+1]%P)%P;
}

int calc(int x,int y,int fx,int fy){
    int l=0,r=std::min(x,n-y+1),z;

    while(l<r){
        z=l+r+1>>1;

        if(H2(fx,x-z+1,x)==H1(fy,y,y+z-1)) l=z;
        else r=z-1;
    }

    return l;
}

signed main(){
    int i,j;
    scanf("%d%s%s",&n,s[0]+1,s[1]+1);

    for(i=pw[0]=1;i<N;i++) pw[i]=pw[i-1]*B%P;
    for(i=0;i<2;i++){
        for(j=1;j<=n;j++) h1[i][j]=(h1[i][j-1]*B+s[i][j])%P;
        for(j=n;j>=1;j--) h2[i][j]=(h2[i][j+1]*B+s[i][j])%P;
    }

    for(i=1;i<=n;i++){
        j=calc(i,i,0,0);
        ans=std::max(ans,(j+calc(i-j,i+j-1,0,1))*2-1);
    }for(i=1;i<n;i++){
        j=calc(i,i+1,0,0);
        ans=std::max(ans,(j+calc(i-j,i+j,0,1))*2);
    }for(i=1;i<=n;i++){
        j=calc(i,i,1,1);
        ans=std::max(ans,(j+calc(i-j+1,i+j,0,1))*2-1);
    }for(i=1;i<n;i++){
        j=calc(i,i+1,1,1);
        ans=std::max(ans,(j+calc(i-j,i+j,0,1))*2);
    }for(i=1;i<=n;i++) ans=std::max(ans,calc(i,i,0,1)*2);

    printf("%d\n",ans);
    return 0;
}