#include<bits/stdc++.h> using namespace std; int main() { long long n,s=0,i,k,m=1,a,b; cin>>a>>b; for(i=a;i<=b;i++) { m=m*i; while(m%10==0) { s++; m=m/10; } m%=1000000000; } cout<<s; return 0; }