How to fine every type password thaty possiable by numeric values In C

#include<stdio.h>
#include<conio.h>
#include<math.h>
void main()
{
int a,b,c,d,e,f,g,h,i;
clrscr();
{
printf("Maybe passward are");
printf("\nminimam value");
scanf("%d",&a);
printf("\nMaxmim value");
scanf("%d",&b);
for(i=a;i<=b;i++)
{
for(h=a;h<=b;h++)
{
for(g=a;g<=b;g++)
{
for(f=a;f<=b;f++)
{
printf("\t%d%d%d%d",i,h,g,f);
}}}}}
getch();
}