#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*ptr=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;
    ptintf("%d",diff);
    return 0;
}