#include<bits/stdc++.h>

using namespace std;

#define il inline

#define ll long long

#define gc getchar()

#define ri register int

#define rc register char

#define rb register bool

#define rp(i,x,y) for(ri i=x;i<=y;++i)

#define my(i,x,y) for(ri i=x;i>=y;--i)

const int mod=,N=+;

int l,r,sum,fac[N],ifac[N];

bool vis[N];

il int read()

{

    rc ch=gc;ri x=;rb y=;

    while(ch!='-' && (ch>'' || ch<''))ch=gc;

    if(ch=='-')ch=gc,y=;

    while(ch>='' && ch<='')x=(x<<)+(x<<)+(ch^''),ch=gc;

    return y?x:-x;

}

il int power(ri x,ri y){int ret=;while(y){if(y&)ret=1ll*ret*x%mod;x=1ll*x*x%mod;y>>=;}return ret;}

il void pre(ri n)

{

    fac[]=;rp(i,,n)fac[i]=1ll*fac[i-]*i%mod;

    ifac[n]=power(fac[n],mod-);my(i,n-,)ifac[i]=1ll*ifac[i+]*(i+)%mod;

}

inline int C(ri n,ri m){return 1ll*fac[n]*ifac[m]%mod*ifac[n-m]%mod;}

int main()

{

//  freopen("4562.in","r",stdin);//freopen("4562.out","w",stdout);

    l=read();r=read();pre(r);

    rp(i,l,r)if(!vis[i]){++sum;for(ri j=i;j<=r;j+=i)vis[j]=;}

    ri as=,n=r-l+;

    rp(i,sum,n)as=(as+1ll*i*sum%mod*C(n-sum,n-i)%mod*fac[n-i]%mod*fac[i-]%mod)%mod;

    printf("%d\n",as);

    return ;

}