write the function of multiplying two three-by-three matrices

#include <iostream>
#include <stdio.h>

using namespace std;

int main()
{
    int a[3][3], b[3][3], c[3][3];
    int i, j, k;

    cout << "Enter matrix A" << endl;
    for (i = 0; i < 3; i++)
    {
        for (j = 0; j < 3; j++)
        {
            cin >> a[i][j];
        }
    }

    cout << "Enter matrix B" << endl;
    for (i = 0; i < 3; i++)
    {
        for (j = 0; j < 3; j++)
        {
            cin >> b[i][j];
        }
    }

    // init c
    for (i = 0; i < 3; i++)
    {
        for (j = 0; j < 3; j++)
        {
            c[i][j] = 0;
        }
    }

    for (i