#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define pir pair<int,int>
#define fi first
#define se second
using namespace std;
inline int re()
{
    char c=getchar();
    int x=0,f=1;
    while(c<'0'||c>'9'){if(c=='-') f=-1;c=getchar();}
    while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
    return x*f;
}
const int N=100010;
int n,q;
char c[N];
vector<int> st[N];
int query(int l,int r)
{
    int sepos=n+1;
    for(int i=1;i<=26;i++)
    {
        if(c[l]-'a'+1==i) continue;
        int p=lower_bound(st[i].begin(),st[i].end(),l)-st[i].begin();
        if(p!=st[i].size()&&st[i][p]<=r) sepos=min(sepos,st[i][p]);
    }
    if(sepos==n+1) return -1;
    int ans=-1;
    for(int i=1;i<=26;i++)
    {
        int pz=upper_bound(st[i].begin(),st[i].end(),r)-st[i].begin();pz--;
        int px=sepos;
        if(c[l]-'a'+1!=i) px=l;
        if(pz<=0||st[i][pz-1]<px) continue;
        int py=lower_bound(st[i].begin(),st[i].end(),(px+st[i][pz]+1)/2)-st[i].begin();
        if(py!=st[i].size()&&py<pz) ans=max(ans,(st[i][pz]-st[i][py])*(st[i][py]-px));
        py--;if(py>=0&&px<=st[i][py]) ans=max(ans,(st[i][pz]-st[i][py])*(st[i][py]-px));
    }
    return ans;
}
signed main()
{
    freopen("Time.in","r",stdin);
    freopen("Time.out","w",stdout);
    n=re();q=re();
    scanf("%s",c+1);
    for(int i=1;i<=n;i++) st[c[i]-'a'+1].pb(i);
    for(int i=1;i<=q;i++)
    {
        int l=re(),r=re();
        printf("%lld\n",query(l,r));
    }
    return 0;
}