구구단

#include <stdio.h>


int main(){
    int s,e,i,j;
    scanf("%d %d",&s,&e);
    if(s<2 || s>9 || e<2 || e>9)
    {    do{
        printf("INPUT ERROR!\n");
        scanf("%d %d",&s,&e);
        }while(s<2 || s>9 || e<2 || e>9);
    }
    if(s>e)
    {
        for(j=1;j<=9;j++){
            for(i=s;i>=e;i--){
                printf("%d * %d = %2d   ",i,j,i*j);
            }
            printf("\n");
        }
    }
    else if(s<=e){
        for(j=1;j<=9;j++){
            for(i=s;i<=e;i++){
                printf("%d * %d = %2d   ",i,j,i*j);
            }
        printf("\n");
        }
    }
    return 0;
}