Why Output limit Exceed?
#include <iostream.h>
#include <string.h>
void main()
{
	char a[100],p[100]="0";
	int n,m,i;
	short mm;
	cin >>a;
	while (strcmp(a,p)!=0)
	{
		n=0;
		for (i=0;i<(int)strlen(a);i++)
		   n=n+a[i]-'0';
		do{
			m=0;
			while (n)
			{
			m=m+(n%10);
			n=n/10;
			}
		n=m;
		}
		while (m>10);
		mm=(short)m;
	    cout <<mm<<endl;
        cin >>a;
	}
}