SEVEN+SEVEN+SIX=TWENTY
68782+68782+650=138214
2*(N+10E+100V+1000E+10000S)+X+10I+100S=Y+10T+100N+1000E+10000W+100000T
=2N+X+10(2E+I)+100(2V+S)+1000(2E)+10000(2S)=Y+10T+100N+1000E+10000W+100000T
2N+X=Y+10a [a≤2]
a+2E+I=T+10b [b≤2]
b+2V+S=N+10c [c≤2]
c+2E=E+10d [d≤1]——c+E=10d
d+2S=W+10T [T≤1]