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#include<stdio.h>
#include<math.h>
#include<string.h>
#define gen sqrt(2.0)
double a[1000][1000];
double dis(int x1,int y1,int x2,int y2) {
	return sqrt(pow(x1-x2,2.0)+pow(y1-y2,2.0));
}
int main() {
//	freopen("input.txt","r",stdin);
//	freopen("output.txt","w",stdout);
	a[0][0]=0;
	double last=a[0][1]=1;
	int k=0;
	int j;
	for(int i=0; i<200; i++) {
		k++;
		for(j=0; j<=k; j++) {
			if(j==0&&k-j==1)
				continue;
			a[j][k-j]=last+gen;
			if(j==0)
				a[j][k-j]-=gen;
			last=a[j][k-j];
			//		printf("%d %d %lf\n",j,k-j,last);
		}
		last+=dis(k,0,0,k+1);
		//	printf("-%lf-%d-%lf-\n",last,k,dis(k-1,0,0,k));
	}
//	printf("%lf\n",a[99][99]);
	int T;
	scanf("%d",&T);
	while(T--) {
		int x1,y1,x2,y2;
		scanf("%d %d %d %d",&x1,&y1,&x2,&y2);
		double sum1=a[x1][y1];
		double sum2=a[x2][y2];
		if(sum2>sum1) {
			printf("%.3lf\n",sum2-sum1);
		} else
			printf("%.3lf\n",sum1-sum2);
	}
	return 0;
}