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#include <iostream>
#include <stdlib.h>
#include <string.h>

using namespace std;

/* function to find and print the longest common
   substring of X[0..m-1] and Y[0..n-1] */
void printLCSubStr(char* X, char* Y, int m, int n)
{
    // Create a table to store lengths of longest common
    // suffixes of substrings.   Note that LCSuff[i][j]
    // contains length of longest common suffix of X[0..i-1]
    // and Y[0..j-1]. The first row and first column entries
    // have no logical meaning, they are used only for
    // simplicity of program
    int LCSuff[m + 1][n + 1];

    // To store length of the longest common substring
    int len = 0;

    // To store the index of the cell which contains the
    // maximum value. This cell's index helps in building
    // up the longest common substring from right to left.
    int row, col;

    /* Following steps build LCSuff[m+1][n+1] in bottom
       up fashion. */
    for (int i = 0; i <= m; i++) {
        for (int j = 0; j <= n; j++) {
            if (i == 0 || j == 0)
                LCSuff[i][j] = 0;

            else if (X[i - 1] == Y[j - 1]) {
                LCSuff[i][j] = LCSuff[i - 1][j - 1] + 1;
                if (len < LCSuff[i][j]) {
                    len = LCSuff[i][j];
                    row = i;
                    col = j;
                }
            }
            else
                LCSuff[i][j] = 0;
        }
    }

    // if true, then no common substring exists
    if (len == 0) {
        return;
    }

    // allocate space for the longest common substring
    char* resultStr = (char*)malloc((len + 1) * sizeof(char));

    // traverse up diagonally form the (row, col) cell
    // until LCSuff[row][col] != 0
    resultStr[len] = '\0';
    while (LCSuff[row][col] != 0) {
        resultStr[--len] = X[row - 1]; // or Y[col-1]

        // move diagonally up to previous cell
        row--;
        col--;
    }
    // required longest common substring
    cout << resultStr;
}

/* Driver program to test above function */
int main()
{
    string x, y;
    cin >> x >> y;
    char* X = new char[x.size()+1]; copy(x.begin(), x.end(), X); X[x.size()] = '\0';
    char* Y = new char[y.size()+1]; copy(y.begin(), y.end(), Y); Y[y.size()] = '\0';

    int m = strlen(X);
    int n = strlen(Y);

    printLCSubStr(X, Y, m, n);
    return 0;
}