C Matrices Multiplication

#include <stdio.h>
int main()
{
int a[10][10], b[10][10];
int num1, num2, num3, num4, i, j, k, res = 0;
printf("Enter the order of matrix A up to (10 x 10)\n");
scanf("%d%d", &num1, &num2);
printf("Enter your Matrix A of order %x %d\n", num1, num2);
for(i = 0; i < num1; i++)
{
for(j=0; j < num2; j++)
{
scanf("%d", &a[i][j]);
}
}
printf("\nEnter the order of matrix B upto (10 x 10)\n");
scanf("%d%d", &num3, &num4);
if(num2 == num3)
{
printf("Enter your Matrix A of order %x %d\n", num3, num4);
for(i = 0; i < num3; i++)
{
for(j = 0; j < num4; j++)
{
scanf("%d", &b[i][j]);
}
}
}
else
{
printf("Sorry matrix of order (%dx%d) * (%dx%d) is impossible", num1, num2, num3, num4);
return 0;
}
printf("\n Matrix Multiplication \n");
for(i = 0; i < num1; i++)
{
for(j = 0; j < num4; j++)
{
for(k = 0; k < num2; k++)
{
res = res + (a[i][k] * b[k][j]);
}
printf("%d ",res);
res = 0;
}
printf("\n");
}
return 0;
}