johnny n the beanstalk-code is rigth but giving wrong answer in one case-plz help

general
,
1

#include <stdio.h>
#include <stdlib.h>

                       int main()
                    {
int t;
scanf("%d",&t);
while(t--)
{
    long long int n=0,b=0,flag=0,i=0,stem=0;
    scanf("%lld",&n);
    scanf("%lld",&b);
    stem=1-b;

    if(b<=1)
    {
        for(i=2;i<=n-1;i++)
        {
            scanf("%lld",&b);
            if(flag==0)
            {
            stem*=2;
            if(b<=stem)
                stem=stem-b;
            else
                flag=1;
            }
        }
        scanf("%lld",&b);
        if(flag==0)
        {
            if(b==(2*stem))
                printf("Yes\n");
            else
                printf("No\n");
        }

        else
            if(flag!=0)
                printf("No\n");


    }
    else
        {printf("No\n");
        continue;}

}
return 0;

}