letter frequency

                                //URI Problem 1255(Level Two)
#include<stdio.h>
#include<string.h>

int main()
{
    int a,b,c,d,e=0,f,g,h,i,z,m;
    char j,x[200],w[200],y[200],zz[]={"abcdefghijklmnopqrstuvwxyz"};
    scanf("%d",&f);
    getchar();
    for(a=0; a<f; a++)
    {
        gets(x);
        e=strlen(x);
        g=0;
        h=0;
        z=2;
        i=0,m=0;
        for(b=0; b<26; b++)
        {
            for(c=0; c<e; c++)
            {
                if(x[c] >= 65 && x[c] <= 90){x[c] += 32;}
                if(x[c]==zz[b])
                {
                    g++;
                }
            }
            if(g==1)
            {
                w[h]=zz[b];
                h++;
            }

            if(g>z)
            {
                z=g;
                j=zz[b];     //cant build the logic..how I can print this...??
            }
            if(g==z)
            {
                //m++;
                if(i==0||zz[b]!=y[i])    //cant build the logic..how can I print this...??
                    y[i]=zz[b];
                i++;
            }
            g=0;//puts(y);
        }
        w[h]='\0';
        y[i]='\0';
        if(z==2)
        {
            puts(w);
        }
        else if(m<z)
        {
            printf("%c\n",j);
        }
        else
        {
            puts(y);
        }

    }
    return 0;
}