#include<cstdio>
#include<cstring>
#include<algorithm>
#define rg register int
#define rep(i,l,r) for (rg i=(l); i<=(r); i++)
using namespace std;const int N=200100;
int n,m,a,b,c,d,nd,h[N],x[N],y[N],s[N],sa[N],rt[N],rk[N],lg[N],ls[N*20],rs[N*20],sm[N*20],st[N][20];
char S[N];void rd(int &x){x=0; char ch=getchar();while (ch<'0' || ch>'9') ch=getchar();while (ch>='0' && ch<='9') x=x*10+ch-'0',ch=getchar();
}bool Cmp(rg l,rg r,rg k){ return l+k<=n && r+k<=n && y[l]==y[r] && y[l+k]==y[r+k]; }void build(rg m){memset(y,0,sizeof(y));rep(i,0,m) s[i]=0;rep(i,1,n) s[x[i]=S[i]-'a'+1]++;rep(i,1,m) s[i]+=s[i-1];for (rg i=n; i; i--) sa[s[x[i]]--]=i;for (rg k=1,p=0; p<n; k<<=1,m=p){p=0;rep(i,n-k+1,n) y[++p]=i;rep(i,1,n) if (sa[i]>k) y[++p]=sa[i]-k;rep(i,0,m) s[i]=0;rep(i,1,n) s[x[y[i]]]++;rep(i,1,m) s[i]+=s[i-1];for (rg i=n; i; i--) sa[s[x[y[i]]]--]=y[i];rep(i,1,n) y[i]=x[i]; p=1; x[sa[1]]=1;rep(i,2,n) x[sa[i]]=Cmp(sa[i],sa[i-1],k)?p:++p;}
}void getheight(){int k=0; rep(i,1,n) rk[sa[i]]=i;rep(i,1,n){for (rg j=sa[rk[i]-1]; i+k<=n && j+k<=n && S[i+k]==S[j+k]; k++);h[rk[i]]=k; if (k) k--;}
}void rmq(){rep(i,1,n) st[i][0]=h[i];rep(j,1,lg[n]) rep(i,1,n-(1<<j)+1) st[i][j]=min(st[i][j-1],st[i+(1<<(j-1))][j-1]);
}void add(int y,int &x,int L,int R,int pos){x=++nd; sm[x]=sm[y]+1; ls[x]=ls[y]; rs[x]=rs[y];if (L==R) return; int mid=(L+R)>>1;if (pos<=mid) add(ls[y],ls[x],L,mid,pos); else add(rs[y],rs[x],mid+1,R,pos);
}int que(int y,int x,int L,int R,int l,int r){if (!x) return 0;if (L==l && r==R) return sm[x]-sm[y];int mid=(L+R)>>1;if (r<=mid) return que(ls[y],ls[x],L,mid,l,r);else if (l>mid) return que(rs[y],rs[x],mid+1,R,l,r);else return que(ls[y],ls[x],L,mid,l,mid)+que(rs[y],rs[x],mid+1,R,mid+1,r);
}int ask(rg l,rg r){ rg t=lg[r-l+1]; return min(st[l][t],st[r-(1<<t)+1][t]); }void getrange(rg x,int &l,int &r,rg mid){l=r=x;for (int i=17; ~i && r<n; i--) if (r+(1<<i)<=n && ask(x+1,r+(1<<i))>=mid) r=r+(1<<i);for (int i=17; ~i && l>1; i--) if (l-(1<<i)>=0 && ask(l-(1<<i)+1,x)>=mid) l=l-(1<<i);
}int jud(rg mid){int l,r; getrange(rk[c],l,r,mid);if (que(rt[l-1],rt[r],1,n,a,b-mid+1)>0) return 1; else return 0;
}int main(){freopen("bzoj4556.in","r",stdin);freopen("bzoj4556.out","w",stdout);scanf("%d%d%s",&n,&m,S+1);lg[1]=0; rep(i,2,n) lg[i]=lg[i>>1]+1;build(30); getheight(); rmq();rep(i,1,n) add(rt[i-1],rt[i],1,n,sa[i]);while (m--){rd(a); rd(b); rd(c); rd(d);if (!jud(1)) { printf("0\n"); continue; }int l=1,r=min(d-c+1,b-a+1),ans=0;while (l<r){int mid=(l+r)>>1;if (jud(mid)) ans=mid,l=mid+1; else r=mid;}if (jud(l)) printf("%d\n",l); else printf("%d\n",ans);}return 0;
}