Mind Reader Game code in c language

#include<stdio.h>
void main()

{
int a,ress;
 printf("think a number between 1-999\n");

    printf("After clicking that number then multiply with 143 and then save it in your mind\n");
 printf("Enter the last three digit which you got after multiply with 143\n");

 printf("Enter the last three digit\n");
 scanf("%s", &a);
if(a>=1&&a<=999)

 {ress= a*7;

 int e,b,c;
 e=ress%10;
 ress=ress/10;
 b=ress%10;
 ress=ress/10;
 c=ress%10;

 printf("You pick this number %s%s%s\n", c,b,e);
return;
}

else
{printf("wrong entry ");}
getch();
}