artificial intelligence - Langtons Ant in C++ (console) - core dumped -

i wrote simple langtons ant in c++ (console). (dont know why) i'm getting core dumped every time run program:

#include <iostream> #include <ctime> #include <cstdlib>  using namespace std;  int main() {     srand(time(null));      bool endgame = false;     enum compass {north, east, south, west};     compass dir = north;     int x = 0, y = 0;     int n = 30, m = 30;      int **board = new int*[n];     for(int = 0; <n; i++)         board[i] = new int[m];      for(int i=0; i<n; i++)         for(int j=0; j<m; j++)             board[i][j] = rand()%2;      long count = 0;     while(!endgame)     {         for(int = 0; < n; i++)         {             for(int j = 0; j < m; j++)             {                 //print board                 if(board[i][j] == 0)                     cout << '+';                 else                     cout << '#';             }             cout << endl;         }          //ant         if (board[x][y] == 0)         {             board[x][y] = 1;             switch (dir){             case north:                 dir = east;                 x = ((x+1)%m);                 break;             case east:                 dir = south;                 y = ((y-1) % n);                 break;             case south:                 dir = west;                 x = ((x-1) % m);                 break;             case west:                 dir = north;                 y = ((y+1) %n);                 break;             }         }else         {             board[x][y] = 0;             switch(dir){             case north:                 dir = west;                 x = ((x-1) % m);                 break;             case west:                 dir = south;                 y = ((y-1) % n);                 break;             case south:                 dir = east;                 x = ((x+1)%m);                 break;             case east:                 dir = north;                 y = ((y+1) %n);                 break;             }         }         cout << endl << count << endl;         count++;         cin.sync();         cin.get();     }     cin.sync();     cin.get();     return 0; } 

how can rid of error?

it's use of modulo this:

x = ((x-1) % m); 

keep in mind negative % positive = negative, meaning can out of bounds.