[joker99]

Ну тогда так

int NumberOfRoutes = 0;
function void countRoutes(int cur)
{
    if (cur == N)
    {
      NumberOfRoutes++; 
      return;
    }
    for(step = 1;step<=M;step++)
    {
       if(cur+step<=N)
          countRoutes(cur+step);
    }
}