Error in discount estimator

[Antoine Ghaoui]

Hello,

When using fngram-count to generate a Language Model, i'm getting the  
following error:

warning: one of required modified KneserNey count-of-count is zero
error in discount estimator


Can someone help?

knowing that the factor file is


## root trigram
1
R : 2 R(-1) R(-2) ntextfile_99.flm.cnt ntextfile_99.flm.lm 3
R1R2    R2      kndiscount gtmin 1 interpolate
R1      R1      kndiscount gtmin 1 interpolate
0       0       kndiscount gtmin 1

Thanks

Antoine