let a be Integer; :: thesis:
let p be Prime; :: thesis:
let b be Integer; :: thesis:
assume that
A1: p > 2 and
A2: a gcd p = 1 and
A3: a,b are_congruent_mod p ; :: thesis:
Lege (a,p),a |^ ((p -' 1) div 2) are_congruent_mod p by A1, A2, Th28;
then A4: (Lege (a,p)) mod p = (a |^ ((p -' 1) div 2)) mod p by NAT_D:64;
b gcd p = 1 by A2, A3, WSIERP_1:43;
then Lege (b,p),b |^ ((p -' 1) div 2) are_congruent_mod p by A1, Th28;
then A5: (Lege (b,p)) mod p = (b |^ ((p -' 1) div 2)) mod p by NAT_D:64;
a mod p = b mod p by A3, NAT_D:64;
then (Lege (a,p)) mod p = (Lege (b,p)) mod p by A4, A5, Th13;
then Lege (a,p), Lege (b,p) are_congruent_mod p by NAT_D:64;
then A6: p divides (Lege (a,p)) - (Lege (b,p)) ;

per cases by Th25;

suppose A7: Lege (a,p) = 1 ; :: thesis:

A8: now :: thesis:

assume Lege (b,p) = 0 ; :: thesis:
then p = 1 by A6, A7, WSIERP_1:15;
hence contradiction by A1; :: thesis:

end;

Lege (b,p) <> - 1 by A7, A1, A6, NAT_D:7;
hence Lege (a,p) = Lege (b,p) by A7, A8, Th25; :: thesis:

end;

suppose A9: Lege (a,p) = 0 ; :: thesis:

A10: now :: thesis:

assume Lege (b,p) = 1 ; :: thesis:
then p = 1 by WSIERP_1:15, A6, A9, INT_2:10;
hence contradiction by A1; :: thesis:

end;

now :: thesis:

assume Lege (b,p) = - 1 ; :: thesis:
then p = 1 by A6, A9, WSIERP_1:15;
hence contradiction by A1; :: thesis:

end;

hence Lege (a,p) = Lege (b,p) by A9, Th25, A10; :: thesis:

end;

suppose A11: Lege (a,p) = - 1 ; :: thesis:

A12: now :: thesis:

assume Lege (b,p) = 1 ; :: thesis:
then p divides - 2 by A6, A11;
then p divides 2 by INT_2:10;
hence contradiction by A1, NAT_D:7; :: thesis:

end;

now :: thesis:

assume Lege (b,p) = 0 ; :: thesis:
then p = 1 by WSIERP_1:15, A6, A11, INT_2:10;
hence contradiction by A1; :: thesis:

end;

hence Lege (a,p) = Lege (b,p) by A11, Th25, A12; :: thesis:

end;

end;