#include <iostream>

using namespace std;

int main()
{
	int n;
    int minim = 10;
    int maxim = -1;
    cin >> n;
    while(n){
        minim = min(minim,n%10);
        maxim = max(maxim,n%10);
        n/=10;
    }
    cout << minim + maxim;
    return 0;
}