1029 Old keyboard, C

#include <stdio.h>

int main()
{   
    int i=0,j=0,k=0,l=0,flag;
	char a[100]={0},b[100]={0};
	char c[100]={0},d[100]={0};
    scanf("%s %s",a,b);
    while(a[i])
    {
        if(a[i] == b[j])
            j++;
        else
        {
            if( (a[i]>96)&&(a[i]<123) )
				c[k] = a[i]-32;
			else
				c[k] = a[i];
            k++;
        }
        i++;
    }
	k=0;i=0;
	while(c[k])
	{
		i=0;
		flag = 1;
		while(d[i])
			{if( d[i] == c[k] )
				flag = 0;
            i++;}
		if(flag)	{d[l] = c[k];	l++;}
		k++;
	}

	printf("%s",d);
    //printf("%s\n%s\n",d,c);
	//system("pause");
    return 0;
}