1: 1997*1998*1999*2000 +1
2: (1997*2000 ) * (1998*1999) + 1
2.1 1997*2000 = 3994000
2.2: 1998*1999 = 1997*2000 + 2 = 3994002
3: 3994000 * 3994002 + 1
3.1 3994000*3994000 + 3994000*2 + 1
4: ( 3994*3994 ) * 1000 * 1000 + 3994000*2 + 1
4.1: [(4000*3988) + 36] * 1000 * 1000 + 3994000*2 + 1
5 : (15952000 + 36) * 1000 * 1000 + 3994000*2 + 1
6: 15952036,000,000 + 7,988,000 + 1
6.1: 15952043,988,000 + 1
7. 15952043,988,001