import java.math.BigInteger;

import java.util.function.LongToDoubleFunction;


/* The four adjacent digits in the 1000-digit number 

 * that have the greatest product are 9 × 9 × 8 × 9 = 5832.


73167176531330624919225119674426574742355349194934

96983520312774506326239578318016984801869478851843

85861560789112949495459501737958331952853208805511

12540698747158523863050715693290963295227443043557

66896648950445244523161731856403098711121722383113

62229893423380308135336276614282806444486645238749

30358907296290491560440772390713810515859307960866

70172427121883998797908792274921901699720888093776

65727333001053367881220235421809751254540594752243

52584907711670556013604839586446706324415722155397

53697817977846174064955149290862569321978468622482

83972241375657056057490261407972968652414535100474

82166370484403199890008895243450658541227588666881

16427171479924442928230863465674813919123162824586

17866458359124566529476545682848912883142607690042

24219022671055626321111109370544217506941658960408

07198403850962455444362981230987879927244284909188

84580156166097919133875499200524063689912560717606

05886116467109405077541002256983155200055935729725

71636269561882670428252483600823257530420752963450


Find the thirteen adjacent digits in the 1000-digit number 

that have the greatest product. What is the value of this product?

*/


public class Problem8 {

private static final String longDigit = 

"73167176531330624919225119674426574742355349194934" + 

"96983520312774506326239578318016984801869478851843" + 

"85861560789112949495459501737958331952853208805511" + 

"12540698747158523863050715693290963295227443043557" + 

"66896648950445244523161731856403098711121722383113" + 

"62229893423380308135336276614282806444486645238749" + 

"30358907296290491560440772390713810515859307960866" + 

"70172427121883998797908792274921901699720888093776" + 

"65727333001053367881220235421809751254540594752243" + 

"52584907711670556013604839586446706324415722155397" + 

"53697817977846174064955149290862569321978468622482" + 

"83972241375657056057490261407972968652414535100474" + 

"82166370484403199890008895243450658541227588666881" + 

"16427171479924442928230863465674813919123162824586" + 

"17866458359124566529476545682848912883142607690042" + 

"24219022671055626321111109370544217506941658960408" + 

"07198403850962455444362981230987879927244284909188" + 

"84580156166097919133875499200524063689912560717606" + 

"05886116467109405077541002256983155200055935729725" + 

"71636269561882670428252483600823257530420752963450";

private BigInteger adjacentProduct(int begin, int nAdjacent) {

char[] subArray = longDigit.substring(begin, begin+nAdjacent).toCharArray();

BigInteger product = new BigInteger("1");

for (char c : subArray) {

product = product.multiply(new BigInteger(String.valueOf(c)));

}

return product;

}

public BigInteger solve(int nAdjacent) {

BigInteger max = new BigInteger("0");

for (int begin=0;  begin <= longDigit.length()-nAdjacent; begin++) {

BigInteger product = adjacentProduct(begin, nAdjacent);

if(product.compareTo(max) > 0) {

max = product;

}

}

return max;

}

public static void main(String[] args) {

//23514624000

System.out.println(new Problem8().solve(13));

}

}