#include <stdlib.h>
    #include <stdio.h>
    #include <sys/time.h>
	const int N = 30;
	const int M = 30;
  int A[N][M] = { 1 }, B[N][M] = { 1 };
    void convo(int A[N][M], int B[N][M])
    {
      for (int i = 1; i < N-1; ++i)
       for (int j = 1; j < M-1; ++j)
        B[i][j] = (A[i][j]*4 + A[i-1][j] +
           A[i+1][j] + A[i][j-1] + A[i][j+1])/8;
	}


    int main(int argc, char** argv)
    {
       int L, i;
       struct timeval tv1, tv2;
       L = atoi(argv[1]);
       gettimeofday(&tv1, 0);
       for (int i = 0; i < L; ++i)
       {
		convo(A, B);
          convo(B, A);
       }
       gettimeofday(&tv2, 0);
       printf("T = %f seconds\n",
              (float)((tv2.tv_usec - tv1.tv_usec)*1e-6
                    + (tv2.tv_sec - tv1.tv_sec)));
return 0; }