uva 1586 Molar mass(Uva-1586)

#include <bits/stdc++.h>
using namespace std;
main()
{
    int a;
    cin>>a;
    while(a--)
    {
        string b="";
        cin>>b;
        stringstream stream;
        int sumc,sumh,sumo,sumn;
        sumc=sumh=sumo=sumn=0;
        int c,h,o,n,f;
        c=h=o=n=0;f=1;
        string str="";
        for(int i=0;i<b.size()+1;i++)
        {
            if(isalpha(b[i])&&isalpha(b[i+1])||isalpha(b[i])&&!b[i+1])
            {
                if(b[i]==‘C‘)
                sumc+=1;
                if(b[i]==‘H‘)
                sumh+=1;
                if(b[i]==‘O‘)
                sumo+=1;
                if(b[i]==‘N‘)
                sumn+=1;    
            }
            else if(isdigit(b[i])&&f)
            {
                if(b[i-1]==‘C‘)
                {
                    str+=b[i];c=1;f=0;
                }
                if(b[i-1]==‘H‘)
                {
                    str+=b[i];h=1;f=0;
                }
                if(b[i-1]==‘O‘)
                {
                    str+=b[i];o=1;f=0;
                }
                if(b[i-1]==‘N‘)
                {
                    str+=b[i];n=1;f=0;
                }
            }    
            else if(c&&!f)
            {
                if(isalpha(b[i])||!b[i])
                {
                    int num=0;
                    f=1;c=0;
                    stream<<str;
                    stream>>num;
                    sumc+=num;
                    stream.clear();
                    str="";
                }
                else
                str+=b[i];
            }
            else if(h&&!f)
            {
                if(isalpha(b[i])||!b[i])
                {
                    int num=0;
                    f=1;h=0;
                    stream<<str;
                    stream>>num;
                    sumh+=num;
                    stream.clear();
                    str="";
                }
                else
                str+=b[i];
            }
            else if(o&&!f)
            {
                if(isalpha(b[i])||!b[i])
                {
                    int num=0;
                    f=1;o=0;
                    stream<<str;
                    stream>>num;
                    sumo+=num;
                    stream.clear();
                    str="";
                }
                else
                str+=b[i];
            }
            else if(n&&!f)
            {
                if(isalpha(b[i])||!b[i])
                {
                    int num=0;
                    f=1;n=0;
                    stream<<str;
                    stream>>num;
                    sumn+=num;
                    stream.clear();
                    str="";
                }
                else
                str+=b[i];
            }
        }    
        double sum=0;
        sum=sumc*12.01+sumh*1.008+sumo*16.00+sumn*14.01;
        printf("%.3lf\n",sum);
    }    
}