#include <stdio.h>
 
void fill_matrix(int rows, int cols, int matrix[rows][cols]) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            matrix[i][j] = i * cols + j;
        }
    }
}
 
int main() {
    int r = 3, c = 4;
    int my_matrix[r][c];
    fill_matrix(r, c, my_matrix);
    printf("Element [2][3]: %d\n", my_matrix[2][3]);
    return 0;
}