#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>

int main(){
    int N;
    scanf("%d",&N);
    
    if(N<=0||N>100){
        printf("Invalid Input");
        return 0;
    }
    char ch;
    int eveSum=0,oddSum=0;
    for(int i=0;i<N;i++){
        scanf(" %c",&ch);
        
        if (!isalpha(ch)){
            printf("Invalid Input");
            return 0;
        }
        if(((int)ch)%2==0)
           evenSum+=(int)ch;
        else
            oddSum += (int)ch;
    }
    int diff=abs(evenSum -oddSum);
    printf("%d",diff);
    
    return 0;
}