C++ :

#include <string>
#include <vector>
#include <cstring>
#include <algorithm>
#include <iostream>

using namespace std;

class TheLuckyGameDivTwo {
    public:
        static const int MAX = 5000;

        int t[MAX];

        bool check(int n) {
            while (n) {
                int d = n%10;
                n /= 10;

                if (d != 4 && d != 7) {
                    return false;
                }
            }
            return true;
        }


        int find(int a, int b, int jLen, int bLen) {
            int ret;

            memset(t, 0, sizeof(t));

            t[a] = check(a);
            for (int i = a+1; i <= b; ++i) {
                t[i] = t[i-1]+check(i);
            }

            ret = -1;
            for (int i = a-1; i <= b-jLen; ++i) {
                int aa = i;
                int bb = i+jLen;

                int cur = 1000005;
                for (int j = aa; j <= bb-bLen; ++j) {
                    int tmp = t[j+bLen]-t[j];
                    cur = min(cur, tmp);
                }
                ret = max(ret, cur);
            }

            return ret;
        }
};
int main(){
  int a,b,jLen,bLen;
  class TheLuckyGameDivTwo solution;
  while(cin>>a>>b>>jLen>>bLen){
    cout<<solution.find(a,b,jLen,bLen)<<endl;
  }
  return 0;
}

Java :

import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner in=new Scanner(System.in);
        int[] ok=new int[5000];
        for(int i=1;i<=4747;i++){
            int p=i;
            while(p>0){
                if(p%10==4||p%10==7)
                    p/=10;
                else {
                    p=-1;
                    break;
                }
            }
            if(p==0) 
                ok[i]=1;
            else
                ok[i]=0;
        }
        int[] sum=new int[5000];
        sum[0]=0;
        for(int i=1;i<=4747;i++){
            if(ok[i]==1){
                sum[i]=sum[i-1]+1;            
            }
            else{
                sum[i]=sum[i-1];
            }
        }
        while(in.hasNext()){
            int a=in.nextInt();
            int b=in.nextInt();
            int jlen=in.nextInt();
            int blen=in.nextInt();
            int Max=sum[a+jlen-1]-sum[a-1];
            for(int i=a+1;i+jlen-1<=b;i++){
                if(sum[i+jlen-1]-sum[i-1]>Max){
                    Max=sum[i+jlen-1]-sum[i-1];
                }
            }
            int ans=0;
            for(int i=a;i+jlen-1<=b;i++){
                if(sum[i+jlen-1]-sum[i-1]==Max){
                    int ans1=sum[i+blen-1]-sum[i-1];
                    for(int j=i+1;j+blen-1<=i+jlen-1;j++){
                        ans1=Math.min(ans1,sum[j+blen-1]-sum[j-1]);
                    }
                    ans=Math.max(ans,ans1);
                }
            }
            System.out.println(ans);
        }
    }
}