The natural constant e is a well known transcendental number（超越数）. The first several digits are: e = 2.718281828459045235360287471352662497757247093699959574966967627724076630353547594571382178525166427427466391932003059921... where the 10 digits in bold are the answer to Google's question.
Now you are asked to solve a more general problem: find the first K-digit prime in consecutive digits of any given L-digit number.
Input Specification:
Each input file contains one test case. Each case first gives in a line two positive integers: L (≤ 1,000) and K (< 10), which are the numbers of digits of the given number and the prime to be found, respectively. Then the L-digit number N is given in the next line.
Output Specification:
For each test case, print in a line the first K-digit prime in consecutive digits of N. If such a number does not exist, output 404 instead. Note: the leading zeroes must also be counted as part of the K digits. For example, to find the 4-digit prime in 200236, 0023 is a solution. However the first digit 2 must not be treated as a solution 0002 since the leading zeroes are not in the original number.
Sample Input 1:
20 5
23654987725541023819
Sample Output 1:
49877
Sample Input 2:
10 3
2468024680
Sample Output 2:
404#include<iostream>
#include<string>
#include<sstream>
#include<vector>
#include<algorithm>
#include<cmath>
using namespace std;
//11:06bool isp(int a)
{if(a<=1) return false;int k=pow(a,0.5);for(int i=2;i<k;i++){if(a%i==0) return false;}return true;
}
int main()
{//freopen("C:\\Users\\chenzhuo\\Desktop\\in.txt","r",stdin);int n,m;cin>>n>>m;string s;cin>>s;for(int i=0;i<=n-m;i++){string str=s.substr(i,m);stringstream ss;ss<<str;int tmp;ss>>tmp;if(isp(tmp)){cout<<str;return 0;}}cout<<"404";}