#include<stdio.h>
#include<string.h>
int main(void){
	char c[10];
	char buf,max= '0';
	int i,j,l,m;
	scanf("%s",c);
	
	for(i=0;i<2;i++){
		for(j=i;j<strlen(c);j++){
			if(max < c[j]){
				m = j;
				max = c[i];
			}
		}
		buf = c[i];
		c[i] = c[m];
		c[m] = buf;
	}
	printf("%s",c);
	return 0;
}