Sgu/170

//by mx
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXN 5000
#define MAX(x,y) ((x)>(y)?(x):(y))
#define ABS(x) (MAX(x,-(x)))
#define MIN(x,y) ((x)<(y)?(x):(y))
#define oo 1e9
#define R return
long n,a[MAXN+10]={0},b[MAXN+10]={0},n1=0,n2=0,ans=0;
char st[MAXN+10]={0};
void init()
{
	long i;
	scanf("%s",st);
	n=strlen(st);
	n1=0;
	for (i=0;i<n;i++)
		if (st[i]=='-') a[++n1]=i;
	scanf("%s",st);
	if (strlen(st)!=n)
	{
		printf("-1\n");
		R;
	}
	n2=0;
	for (i=0;i<n;i++)
		if (st[i]=='-') b[++n2]=i;
	if (n1!=n2)
	{
		printf("-1\n");
		R;
	}
	ans=0;
	for (i=1;i<=n1;i++)
	    ans+=ABS(a[i]-b[i]);
	printf("%ld\n",ans);
	R;
}
int main()
{
	init();
	R 0;
}