Find the modulo 7 remainder of the sum 1+3+5+7...+197+199
N = [199 -1] / 2 + 1 = 100 terms
S =[F + L] / 2 x N
S =[1 + 199] / 2 x 100 =10,000
Or: N^2 =100^2 =10,000
10,000 mod 7 = 4
+166 
