#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 evenSum = 0, oddSum =0;
    char *p = arr;
    for(int i=0;i<N;i++)
    {
        if(!isalpha(*(ptr + i)))
        {
            printf("Invalid input");
            return 0;
        }
        if(*(ptr + i) %2 ==0)
        evenSum +=*(ptr + i);
        else
        oddSum += *(ptr + i);
        }
        int diff = evenSum - oddSum;
        if (diff < 0) diff =-diff;
        printf("%d",diff);
        return 0;
    }