#include <stdio.h>

int main(void) {

    long int num;
    
    printf("Hello world!\n");
    printf("num=%ld\n", num);

    printf("%zu\n",sizeof(char));
    printf("%zu\n",sizeof(int));
    printf("%zu\n",sizeof(long));
    printf("%zu\n",sizeof(short));
    printf("%zu\n",sizeof(float));
    printf("%zu\n",sizeof(double));

    printf("%dx%d=%d\n",4,5,20);
    printf("%dx%d=%d\n",7,9,63);

    return 0;
}