zoj 2351 Litmus Test

#include<stdio.h>#include<math.h>int main(){int N,i,j,m,n;double k1,k2,PH,x;scanf("%d",&N);for(i = 1;i<=N;i++){getchar();for(j = 1;;j++){scanf("%lf%lf",&k1,&k2);scanf("%d%d",&m,&n);if(k1==0&&k2==0&&m==0&&n==0)break;x = (sqrt(k1*k1+4*m*n*k1*k2)-k1)/2/n;    PH = -1*log(x)/log(10);printf("%.3lfn",PH);}if(i!=N)printf("n");}return 0;}