1 digit number!!!

/// asa kori ei code a idea ta apner prob solve korbe!!!!


#include<stdio.h>
#include<math.h>
int main()
{
    int output,x=100;
    output=129780; /// apner output......
    while(x/10)
    {
        x=0;
        while(output)
        {
            x=x+output%10;
            output=output/10;
        }
        output=x;
    }
    printf("%d\n",x);
    return 0;
}