C program that reads in a matrix of integers from a file and performs matrix multiplication

#include <stdio.h>
#include <stdlib.h>

#define MAX_SIZE 100

int main()
{
    FILE *fp;
    int a[MAX_SIZE][MAX_SIZE], b[MAX_SIZE][MAX_SIZE];
    int m, n, p, q, i, j, k;

    fp = fopen("matrix.txt", "r");
    if (fp == NULL)
    {
        printf("Error opening file\n");
        return 1;
    }

    fscanf(fp, "%d%d", &m, &n);
    for (i = 0; i < m; i++)
        for (j = 0; j < n; j++)
            fscanf(fp, "%d", &a[i][j]);

    fscanf(fp, "%d%d", &p, &q);
    for (i = 0; i < p; i++)
        for (j = 0; j < q; j++)
            fscanf(fp, "%d", &b[i][j]);

    fclose(fp);

    if (n != p)
    {
        printf("Invalid matrices\n");
        return 1;
    }

    int c[MAX_SIZE][MAX_SIZE];
    for (i = 0; i < m; i++)
        for (j = 0; j < q; j++)
        {
            c[i][j] = 0;
            for (k = 0; k < n; k++)
                c[i][j] += a[i][k] * b[k][j];
        }

    printf("Resulting matrix:\n");
    for (i = 0; i < m; i++)
    {
        for (j = 0; j < q; j++)
            printf("%d ", c[i][j]);
        printf("\n");
    }

    return 0;
}