//idea: remove every right most zero
public class RightMostDigitOfFactorial{

public static int findRightMost(long n){
     System.out.println(".....................");
     long rmd = 1;
     long f = 1;
     for(long i= 2;i<=n;i++){
            long b = i;
            // ignore all right most zeros from b
            while(b % 10 == 0) b /= 10;
            f = f * i;
            // ignore all right most zeros from f
            while( f % 10 == 0) f/=10;
            // don't make f exceed 9999 i.e, keep track
           // of only 4 right most digits.
            if( f > 10000) f %= 10000;
     } 
     return (int) f % 10 ;
} 
}