i don't know what's wrong with my program, it looks perfect
but get WA

#include<iostream.h>

#define EOLN '\n'

int res[37];

void main()
{
    int k;
    int maxk = 2;
    char c;
    for (k=2; k<=36; k++)
          res[k] = 0;
    while ((c = cin.get())!=EOLN && c!=EOF)
    {
        for (k=maxk; k<=36; k++)
        {
            int a = 0;
            if ( c >= 'A' && c<= 'Z')
                a = c - 'A' + 10;
            if ( c >= '0' && c<= '9')
                a = c - '0';
            if ( a > maxk - 1 ) maxk = a + 1;
            res[k] = (res[k]*k + a)%(k-1);
        }
    }
    for (k=maxk; k<=36; k++)
          if (res[k] == 0) break;
    if (k<=36)
        cout<<k<<endl;
    else
        cout<<"No Solution\n";
}

Just change "No Solution"  to "No solution.", and you'll
get AC.
You should be very careful and attentive when reading the
task.

Good luck!