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Function: unsigned long int mpz_gcd_ui (mpz_t rop , const mpz_t op1 , unsigned long int op2 ) ¶ Compute the greatest common divisor of op1 and op2 . If rop is not NULL , store the result there. If the result is small enough to fit in an unsigned long int , it is
returned. If the result does not fit, 0 is returned, and the result is equal
to the argument op1 .