为什么要乘以2？

#include<stdio.h>
int main()
{
	int n,y,i,j,k;
	char x,c,v;
	char A[27],a[27];
	for(c='A',i=1,v='a';v<='z',i<=26,c<='Z';v++,i++,c++){
		A[i]=c;
		a[i]=v;
	}
	scanf("%d",&n);
	for(j=0;j<2*n;j++){
		scanf("%c %d",&x,&y);
		printf("j=%d  ",j);
		for(i=1;i<=26;i++){
			if(x==A[i]){
				printf("%d\n",i+y);
		    	break;
		   	}
		}		
		for(k=1;k<=26;k++){
			if(x==a[k]){
				printf("%d\n",-k+y);
				break;
			}
		}
	}
	return 0;
 }