新版本的molar mass(uva-1586)明明debug过了，各种测试还是WA真是气死我了

#include <bits/stdc++.h>
using namespace std;
double trans(string a)
{
	stringstream ss;
	ss<<a;
	double t;
	ss>>t;
	return t;
}
double k[250];
main()
{
	int n;
	cin>>n;
	k['O']=16.00;k['N']=14.01;
	k['H']=1.008;k['C']=12.01;
	while(n--)
	{
		string a;
		cin>>a;
		a=a+'K';
		string st="";
		double sum=0;
		char ch=a[0];
		for(int i=0;i<a.size();i++)
		{
			if(isalpha(a[i]))
			{
				double num=trans(st);
				if(i&&st=="")
				sum+=k[ch];
				else
				sum+=k[ch]*num;
				ch=a[i];
				st=""; 
			}
			if(isdigit(a[i]))
			st=st+a[i];	
		}
		printf("%.3lf
",sum);
	}
}