///长度不小于 k 的公共子串的个数/* 单调队列优化 1 aa 1 2 ab 1 3 abc 2 4 ad 1*/#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>using namespace std;const int MAXN=2222222;char s1[MAXN],s2[MAXN];int r[MAXN],lcp[MAXN],num;int wa[MAXN], wb[MAXN], wv[MAXN], tmp[MAXN],a[MAXN],sum[MAXN];int sa[MAXN]; //index range 1~n value range 0~n-1int cmp(int *r, int a, int b, int l){ return r[a] == r[b] && r[a + l] == r[b + l];}void da(int *r, int *sa, int n, int m){ int i, j, p, *x = wa, *y = wb, *ws = tmp; ///对r中长度为1的子串进行基数排序 for (i = 0; i < m; i++) ws[i] = 0; for (i = 0; i < n; i++) ws[x[i] = r[i]]++; for (i = 1; i < m; i++) ws[i] += ws[i - 1]; for (i = n - 1; i >= 0; i--) sa[--ws[x[i]]] = i; ///对r中长度为j的子串进行基数排序 for (j = 1, p = 1; p < n; j *= 2, m = p) { for (p = 0, i = n - j; i < n; i++) y[p++] = i; for (i = 0; i < n; i++) if (sa[i] >= j) y[p++] = sa[i] - j; for (i = 0; i < n; i++) wv[i] = x[y[i]]; for (i = 0; i < m; i++) ws[i] = 0; for (i = 0; i < n; i++) ws[wv[i]]++; for (i = 1; i < m; i++) ws[i] += ws[i - 1]; for (i = n - 1; i >= 0; i--) sa[--ws[wv[i]]] = y[i]; for (swap(x, y), p = 1, x[sa[0]] = 0, i = 1; i < n; i++) x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++; }}int rank[MAXN]; //index range 0~n-1 value range 1~nint height[MAXN]; //index from 1 (height[1] = 0)void calheight(int *r, int *sa, int n){ int i, j, k = 0; for (i = 1; i <= n; ++i) rank[sa[i]] = i; for (i = 0; i < n; height[rank[i++]] = k) for (k ? k-- : 0, j = sa[rank[i] - 1]; r[i + k] == r[j + k]; ++k); return;}int main(){ //freopen("//media/学习/ACM/input.txt","r",stdin); while (~scanf("%d",&num),num) { scanf("%s%s",s1,s2); int i,j,k=0,res,n,m,l,rr; long long len=0,ans; n=strlen(s1); for (i=0;i<n;i++) { r[k++]=s1[i]; } r[k++]='$'; m=strlen(s2); for (i=0;i<m;i++) { r[k++]=s2[i]; }r[k++]=0; da(r, sa, k,256); calheight(r, sa, k-1); for(l=rr=0,ans=0,i=1;i<k;i++) { if(height[i]<num)l=rr=ans=0; else { res=0; if(sa[i-1]<n) { res=1; ans+=height[i]-num+1; } while(l<rr&&lcp[rr]>height[i]) { ans-=sum[rr]*(lcp[rr]-height[i]); res+=sum[rr--]; } lcp[++rr]=height[i]; sum[rr]=res; if(sa[i]>n) { len+=ans; } } } for(l=rr=ans=0,i=1;i<k;i++) { if(height[i]<num)l=rr=ans=0; else { res=0; if(sa[i-1]>n) { res=1; ans+=height[i]-num+1; } while(l<rr&&lcp[rr]>height[i]) { ans-=sum[rr]*(lcp[rr]-height[i]); res+=sum[rr--]; } lcp[++rr]=height[i]; sum[rr]=res; if(sa[i]<n) { len+=ans; } } } printf("%lld\n",len); } return 0;}
