GP/PARI中，数论库，求离散对数函数znlog的调用

官方给的说明是：znlog(x,g,{o}): return the discrete logarithm of x in (Z/nZ)* in base g. If present, o represents the multiplicative
order of g. Return [ ] if no solution exist.
输入znlog(2,3,5)、znlog(2,3,5)、znlog(2,3,{5})
都会报错： znlog: incorrect type in znlog (t_INT).
明明是整型为什么会报错说类型不对？这个函数该怎么调用？