#include<stdio.h>
#include<ctype.h>
int main(){
    int N;
    scanf("%d",&N);
    if(N<0){
        printf("Invalid input");
        return 0;
    }
    char arr[200];
    int*ptr_even=0,*ptr_odd=0;
    ptr_even= &ptr_even;
    ptr_odd= &ptr_odd;
    int sum_even=0,sum_odd=0;
    for(int i=0;i<N;i++){
        scanf("%c",&arr[i]);
        if(!isalpha(arr[i])){
            printf("Invalid input");
            return 0;
        }
        char*p=&arr[i];
        if((*p%2)==0)
            sum_even +=*p;
        else
            sum_odd +=*p;
    }
    int diff=sum_even-sum_odd;
    if(diff<0)diff=-diff;
    printf("%d",diff);
    return 0;
}