#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;
}