#include<cstdio>
#include<algorithm>
using namespace std;
int gi()
{
    int x=0,w=1;char ch=getchar();
    while ((ch<'0'||ch>'9')&&ch!='-') ch=getchar();
    if (ch=='-') w=0,ch=getchar();
    while (ch>='0'&&ch<='9') x=(x<<3)+(x<<1)+ch-'0',ch=getchar();
    return w?x:-x;
}
const int N = 1e5+5;
char s[N];
int n,m,a[N],T[N],X[N],Y[N],SA[N],Rank[N],Height[19][N],lg[N];
bool cmp(int i,int j,int k){return Y[i]==Y[j]&&Y[i+k]==Y[j+k];}
void getSA()
{
    int m=30;
    for (int i=1;i<=n;++i) ++T[X[i]=a[i]];
    for (int i=1;i<=m;++i) T[i]+=T[i-1];
    for (int i=n;i>=1;--i) SA[T[X[i]]--]=i;
    for (int k=1;k<=n;k<<=1)
    {
        int p=0;
        for (int i=0;i<=m;++i) Y[i]=0;
        for (int i=n-k+1;i<=n;++i) Y[++p]=i;
        for (int i=1;i<=n;++i) if (SA[i]>k) Y[++p]=SA[i]-k;
        for (int i=0;i<=m;++i) T[i]=0;
        for (int i=1;i<=n;++i) ++T[X[Y[i]]];
        for (int i=1;i<=m;++i) T[i]+=T[i-1];
        for (int i=n;i>=1;--i) SA[T[X[Y[i]]]--]=Y[i];
        swap(X,Y);
        X[SA[1]]=p=1;
        for (int i=2;i<=n;++i) X[SA[i]]=cmp(SA[i],SA[i-1],k)?p:++p;
        if (p>=n) break;m=p;
    }
    for (int i=1;i<=n;++i) Rank[SA[i]]=i;
    for (int i=1,j=0;i<=n;++i)
    {
        if (j) --j;
        while (a[i+j]==a[SA[Rank[i]-1]+j]) ++j;
        Height[0][Rank[i]]=j;
    }
    for (int j=1;j<19;++j)
        for (int i=1;i+(1<<j-1)<=n;++i)
            Height[j][i]=min(Height[j-1][i],Height[j-1][i+(1<<j-1)]);
}
struct president_tree{int ls,rs,sum;}t[N*40];int rt[N],tot;
void modify(int &x,int l,int r,int p)
{
    t[++tot]=t[x];t[x=tot].sum++;
    if (l==r) return;int mid=l+r>>1;
    if (p<=mid) modify(t[x].ls,l,mid,p);
    else modify(t[x].rs,mid+1,r,p);
}
int query(int A,int B,int l,int r,int ql,int qr)
{
    if (l>=ql&&r<=qr) return t[B].sum-t[A].sum;
    int mid=l+r>>1,s=0;
    if (ql<=mid) s+=query(t[A].ls,t[B].ls,l,mid,ql,qr);
    if (qr>mid) s+=query(t[A].rs,t[B].rs,mid+1,r,ql,qr);
    return s;
}
int lcp(int l,int r)
{
    if (l==r) return (int)1e9;
    ++l;int k=lg[r-l+1];
    return min(Height[k][l],Height[k][r-(1<<k)+1]);
}
bool check(int MID,int x,int y,int u)
{
    int l,r,up,down;
    l=1;r=Rank[u];
    while (l<r)
    {
        int mid=l+r>>1;
        if (lcp(mid,Rank[u])>=MID) r=mid;
        else l=mid+1;
    }
    up=l;
    l=Rank[u];r=n;
    while (l<r)
    {
        int mid=l+r+1>>1;
        if (lcp(Rank[u],mid)>=MID) l=mid;
        else r=mid-1;
    }
    down=l;
    return query(rt[up-1],rt[down],1,n,x,y-MID+1);
}
int main()
{
    n=gi();m=gi();lg[0]=-1;
    for (int i=1;i<=n;++i) lg[i]=lg[i>>1]+1;
    scanf("%s",s+1);
    for (int i=1;i<=n;++i) a[i]=s[i]-'a'+1;
    getSA();
    for (int i=1;i<=n;++i) rt[i]=rt[i-1],modify(rt[i],1,n,SA[i]);
    while (m--)
    {
        int x=gi(),y=gi(),u=gi(),v=gi();
        int l=0,r=min(y-x+1,v-u+1);
        while (l<r)
        {
            int mid=l+r+1>>1;
            if (check(mid,x,y,u)) l=mid;
            else r=mid-1;
        }
        printf("%d\n",l);
    }
    return 0;
}