求助,SAM 30pts WA

#include<iostream>
#include<cstring>
#include<cstdio>
#include<map>
using namespace std;
const int N = 2e7 + 5;
int n, m;
map<char, int>mp;
char s[N], c[N], ch[N][5];
int lst = 1, cnt = 1, fa[N], len[N];
void insert(int c){
    int p = lst, np = lst = ++cnt;
    len[np] = len[p] + 1;
    for(; p && !ch[p][c]; p = fa[p]) ch[p][c] = np;
    if(!p) fa[np] = 1;
    else{
        int q = ch[p][c];
        if(len[q] == len[p] + 1) fa[np] = q;
        else{
            int nq = ++cnt;
            memcpy(ch[nq], ch[q], sizeof(ch[nq]));
            fa[nq] = fa[q];
            len[nq] = len[p] + 1;
            fa[q] = fa[np] = nq;
            for(;p && ch[p][c] == q; p = fa[p]) ch[p][c] = nq;
        }
    }
}
int main(){
    scanf("%d%d", &n, &m);
    mp['E'] = 0, mp['S'] = 1, mp['W'] = 2, mp['N'] = 3;
    scanf("%s", s + 1);
    for(int i = 1; i <= n; i++) insert(mp[s[i]]);
    while(m--){
        scanf("%s", c + 1);
        int len = strlen(c + 1);
        int now = 1, ans = 0;
        for(int i = 1; i <= len; i++){
            if(ch[now][mp[c[i]]]) now = ch[now][mp[c[i]]], ans++;
            else break;
        }
        printf("%d\n", ans);
    }
    return 0;
}