Răspuns:
abcd=5031, n=7
Explicație pas cu pas:
abcd+a+b+c+d= n!
abcd+a+b+c+d=1001*a+101*b+11c+2d
=> 1001≤1001*a+101*b+11c+2d≤10035
(pentru minim am luat a=1, b=c=d=0; pentru maxim am luat a=b=c=d=9)
=> 1001≤ n! ≤10035
=> n=7
7!=1*2*3*4*5*6*7=5040
1001*a+101*b+11c+2d=5040
=> a=5
5005+101*b+11c+2d=5040
101*b+11c+2d=5040-5005
101*b+11c+2d=35
=> b=0
11c+2d=35
=> c=3; d=1
abcd=5031
verificare: 5031+5+0+3+1=5040=7!
