function main(args)

'reinit'
mes=subwrd(args,1)
df=subwrd(args,2)
ctl=subwrd(args,3)
var=subwrd(args,4)
out=subwrd(args,5)

vari=substr(var,2,3)

'sdfopen MERGE_CPTEC_spi_pearson_01.nc'
'set lon -81.95  -34.65'
'set lat -56.15   12.85'
'open  ' ctl

ano=2000
while (ano<=2021)
 if (mes=feb) 
   if ( (math_mod(ano,4)=0) & (math_mod(ano,400)!=0) | (math_mod(ano,400)=0) )  
     df=29
   else
     df=28
   endif
 endif
 'set dfile 2'
 'set lon -81.95  -34.65'
 'set lat -56.15   12.85'
 'set time 12Z01'mes%ano
 'define tmt=ave('var'.2,time=12z01'mes''ano',time=12z'df''mes''ano')'
 'set dfile 1'
 'set lon -81.95  -34.65'
 'set lat -56.15   12.85'
 'set time 12Z01'mes%ano
 'tm=lterp(tmt,spi_pearson_01.1(t=1))'
 'set gxout stat'
 'd tm'
 n_undef=sublin(result,7)
 n_valid=subwrd(n_undef,4)
 if (n_valid >156513)
  say ano"  "mes"  "df
 'set sdfwrite -nc4 -zip  -3dt ' out'_'ano'_'mes'.nc'
 'sdfwrite tm'
 endif
 ano=ano+1
endwhile

'quit'
return