较快，复制就行，没事

#include<ostream>
#define o int
o l,r,ans;o calc(o x){o y=0;while(x){if(x%10==2)y;x/=10;}return y;}o main(){scanf("%d%d",&l,&r);for(o i=l;i<=r;i)ans+=calc(i);printf("%d",ans);}