#include<stdio.h>main(){ int m,n,i,j,k,s=0,q=0; scanf("%d %d",&m,&n); for(i=m;i<=n;i++){ for(j=1,k=0;j<=i;j++) if(i%j==0) k=k+1; if(k==2) s=s+i; } printf("%d",s);}