#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 100010
using namespace std;
char s[N],A[N],B[N];
int K,na,nb,n,m,i,j,rk[N],sa[N],height[N],tmp[N],cnt[N],Log[N],f[17][N],c[15],ans;
void suffixarray(int n,int m){int i,j,k;n++;for(i=0;i<n;i++)cnt[rk[i]=s[i]]++;for(i=1;i<m;i++)cnt[i]+=cnt[i-1];for(i=0;i<n;i++)sa[--cnt[rk[i]]]=i;for(k=1;k<=n;k<<=1){for(i=0;i<n;i++){j=sa[i]-k;if(j<0)j+=n;tmp[cnt[rk[j]]++]=j;}sa[tmp[cnt[0]=0]]=j=0;for(i=1;i<n;i++){if(rk[tmp[i]]!=rk[tmp[i-1]]||rk[tmp[i]+k]!=rk[tmp[i-1]+k])cnt[++j]=i;sa[tmp[i]]=j;}memcpy(rk,sa,n*sizeof(int));memcpy(sa,tmp,n*sizeof(int));if(j>=n-1)break;}for(j=rk[height[i=k=0]=0];i<n-1;i++,k++)while(~k&&s[i]!=s[sa[j-1]+k])height[j]=k--,j=rk[sa[j]+1];
}
inline int ask(int x,int y){int k=Log[y-x+1];return min(f[k][x],f[k][y-(1<<k)+1]);
}
inline int lcp(int x,int y){if(x>=na||y>=nb)return 0;x=rk[x],y=rk[y+na+1];if(x>y)swap(x,y);return ask(x+1,y);
}
inline void col(int l,int r){if(l<i)l=i;if(r>=nb)r=nb-1;c[l-i-na+K+2]++,c[r-i-na+K+3]--;
}
void dfs(int x,int y,int z){int t=lcp(x,y);x+=t,y+=t;if(x==na||y==nb){int c=K-(z+na-x);if(c>=0)col(y-1-c,y-1+c);return;}if(z==K)return;z++;dfs(x+1,y,z);dfs(x,y+1,z);dfs(x+1,y+1,z);
}
int main(){scanf("%d%s%s",&K,A,B);na=strlen(A),nb=strlen(B);for(i=0;i<na;i++)s[n++]=A[i];s[n++]='#';for(i=0;i<nb;i++)s[n++]=B[i];suffixarray(n,128);for(i=2;i<=n;i++)Log[i]=Log[i>>1]+1;for(i=1;i<=n;i++)f[0][i]=height[i];for(j=1;j<17;j++)for(i=1;i+(1<<j-1)<=n;i++)f[j][i]=min(f[j-1][i],f[j-1][i+(1<<j-1)]);for(m=2*K+1,i=0;i<nb;i++){for(j=1;j<=m;j++)c[j]=0;dfs(0,i,0);for(j=1;j<=m;j++)if(c[j]+=c[j-1])ans++;}return printf("%d",ans),0;
}