Ввести с клавиатуры матрицу 4*4 и подсчитать ее определитель — C++(Си)

#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <alloc.h>
 
float mat(float **a)
{
   int i, j;
   float s, d, f, g, det;
   i=0;
   j=0;
   s=((a[i+2][j+2]*a[i+3][j+3]-a[i+2][j+3]*a[i+3][j+2])*a[i+1][j+1]-(a[i+2][j+1]*a[i+3][j+3]-a[i+2][j+3]*a[i+3][j+1])*a[i+1][j+2]+(a[i+2][j+1]*a[i+3][j+2]-a[i+2][j+2]*a[i+3][j+1])*a[i+1][j+3]);
   d=((a[i+2][j+2]*a[i+3][j+3]-a[i+2][j+3]*a[i+3][j+2])*a[i+1][j]-(a[i+2][j]*a[i+3][j+3]-a[i+2][j+3]*a[i+3][j])*a[i+1][j+2]+(a[i+2][j]*a[i+3][j+2]-a[i+2][j+2]*a[i+3][j])*a[i+1][j+3]) ;
   f=((a[i+2][j+1]*a[i+3][j+3]-a[i+2][j+3]*a[i+3][j+1])*a[i+1][j]-(a[i+2][j]*a[i+3][j+3]-a[i+2][j+3]*a[i+3][j])*a[i+1][j+1]+(a[i+2][j]*a[i+3][j+1]-a[i+2][j+1]*a[i+3][j])*a[i+1][j+3]);
   g=((a[i+2][j+1]*a[i+3][j+2]-a[i+2][j+2]*a[i+3][j+1])*a[i+1][j]-(a[i+2][j]*a[i+3][j+2]-a[i+2][j+2]*a[i+3][j])*a[i+1][j+1]+(a[i+2][j]*a[i+3][j+1]-a[i+2][j+1]*a[i+3][j])*a[i+1][j+2]);
   det=(s*a[i][j])-(d*a[i][j+1])+(f*a[i][j+2])+(g*a[i][j+3]);
 
   return det;
}
 
void main ()
{
   clrscr();
   float **b,z;
   int i,j;
 
   b = (float**)calloc(4, sizeof(float*));
   for (i = 0; i < 4; i++)
      b[i] = (float*)calloc(4, sizeof(float));
 
   for (i = 0; i < 4; i++)
   {
      for (j = 0; j < 4; j++)
      {
         scanf("%f",&b[i][j]);
      }
   }
   z=mat(b);
   printf("%.2f",z);
   for (i = 0; i < 4; i++)
      free(b[i]);
   free(b);
   getch();
}