multiplication of two matrix using threads(i need help plz )

3 4
1 2 3
1 2 3
1 2 3
4 2
5 6
5 6
5 6
5 6

#include <cstdlib>
#include <math.h>
#include <iostream>
#include <stdio.h>
#include <windows.h>
using namespace std;
DWORD i,j,k;
int dim;
struct param {
       int x;
       int y;
       };
 int MAT1[10][10];
 int MAT22[10][10];
 int MAT3[10][10];
 int r1,c1,r2,c2;
      
DWORD WINAPI product(LPVOID S){   
     param *p1=(param *)S;
for(i=0;i<r1;i=i+2)
{
for(j=0;j<c2;j++)
{
for(k=0;k<c1;k++)
{   
    MAT3[i][j]+=MAT1[i][k]*MAT22[k][j];
}
}
}
return 0;
};
int main(int argc, char *argv[])
{                      
    HANDLE ThreadHandle;
    
param *p1=new param;
    DWORD ThreadId;
p1->x=i;
p1->y=j;
    
printf("enter dim of mat1:\n");
scanf("%d%d",&r1,&c1);
for(i=0;i<r1;i++)
{
for(j=0;j<c1;j++)
{
printf("enter mat1[%d][%d]:",i,j);
scanf("%d",&MAT1[i][j]);
}
}
    printf("\n");
    printf("enter dim of mat2:\n");
    scanf("%d%d",&r2,&c2);
    for(i=0;i<r2;i++)
    {
    for(j=0;j<c2;j++)
    {
        printf("enter mat2[%d][%d]:",i,j);
        scanf("%d",&MAT22[i][j]);
}
}
      
if (c1=r2)
{
for(i=0;i<r1;i+2)
{
for(j=0;j<c2;j+2)
{
                 MAT3[i][j]=0;
}
}
 
 ThreadHandle = CreateThread(
  NULL, // default security attributes
  0, //default stack size
     product, //thread function
  &p1, //parameters to thread function
  0, //default creation flags
  &ThreadId);//returns the thread identifier
 //Check of thread is created
 
 
for(i=0;i<r1;i=i+2)
{
for(j=0;j<c2;j++)
{
for(k=0;k<c1;k++)
{   
    MAT3[i][j]+=MAT1[i][k]*MAT22[k][j];
}}}return 0;
 
 if(ThreadHandle != NULL)
  {
   WaitForSingleObject(ThreadHandle, INFINITE);
   CloseHandle(ThreadHandle);
 }
 
}
 
                 
 
  
  printf("\n matrix1 \n");
for(i=0;i<r1;i++)
{
for(j=0;j<c1;j++)
{
printf("%d \t",MAT1[i][j]);
}
printf("\n");
}
printf("\n matrix2 \n");
for(i=0;i<r2;i++)
{
for(j=0;j<c2;j++)
{
printf("%d \t",MAT22[i][j]);
}
printf("\n");
}
printf("\n multiplication of mat...\n");
for(i=0;i<r1;i++)
{
for(j=0;j<c2;j++)
{
printf("%d \t",MAT3[i][j]);
}
printf("\n");
}
}