萌新求助，朴素Gauss消元，WA on #8

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>

using namespace std;

const int N=61;
const int inf=1e9;
const double eps=1e-8;

double a[N][N],b[N],ans[N];
int n,fl;

int main(){
	
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++) scanf("%lf",&a[i][j]);
		scanf("%lf",&b[i]);
	}
	
	fl=-1;
	for(int i=1;i<=n;i++){
		
		int now=i;
		for(int j=i+1;j<=n;j++)
		if(a[j][i]>a[i][i]) now=j;
		
		for(int j=1;j<=n;j++) swap(a[i][j],a[now][j]);
		swap(b[i],b[now]);
		
		if(abs(a[i][i])<eps){
//			fl=i;
			continue;
		}
		
		for(int j=i+1;j<=n;j++){
			
			double p=a[j][i]/a[i][i];
			for(int k=i;k<=n;k++)
				a[j][k]-=a[i][k]*p;
			b[j]-=b[i]*p;
		}
	}
	
	for(int i=n;i>=1;i--){
		
		if(abs(a[i][i])<eps){
			if(abs(b[i])>eps){
				puts("-1");
				return 0;
			}
			else{
				puts("0");
				return 0;
			}
		}
		
		ans[i]=b[i]/a[i][i];
		for(int j=1;j<i;j++)
			b[j]-=a[j][i]*ans[i];
		
	}
	
	for(int i=1;i<=n;i++)
		printf("x%d=%.2lf\n",i,ans[i]);
	
	return 0;
}