#include<stdio.h>
#include<ctype.h>
int main() 
{
    int n;
    scanf("%d",&n);
    if(n<=0 ||n>100)
    {
        printf("Invalid input");
        return 0;
    }
    char arr[n];
    for (int i=0;i<n;i++)
     {
      scanf(" %c",&arr[i]);  
    }
    int es=0; os=0;
    char *ptr = arr;
    for(int i=0;i<n;i++)
    {
        if(isalpha(*(ptr + i)))
        {
            printf("Invalid input");
            return 0;
        }
        if(*(ptr + i) %2==0)
        es+=*(ptr+i);
        else
        os += *(ptr+i);
    }
    int diff=es-os;
    if(diff<0) diff=-diff;
    printf("%d",diff);
    return 0;
}