include <stdio.h>

int main() {

int n;
int dv=0, ch, d; 
scanf("%d",&n);

if (n < 100 && n > 999)
{
	printf("None");
}
else 
{	d = n;
	while(d > 0)
	{
		dv = d % 10;
		ch = ch *10 + dv;
		d = d / 10;
	}
	printf("%d",ch);
}
 

return 0; 

}