Math problemo

#Determine the number of positive integers x, where x is
#less than equal to 9,999,999 and the sum of the digits in x is 31.
a=0
b=0
c=0
d=0
e=0
f=0
g=0
solution=0

while 1000000*a+100000*b+10000*c+1000*d+100*e+10*f+g<=9999999:
    if a+b+c+d+e+f+g==31:
        solution+=1
    if g<9:
       g+=1
    else:
        if f<9:
            f+=1
        else:
            f=0
            if e<9:
                e+=1
            else:
                e=0
                if d<9:
                    d+=1
                else:
                    d=0
                    if c<9:
                        c+=1
                    else:
                        c=0
                        if b<9:
                            b+=1
                        else:
                            b=0
                            if a<9:
                                a+=1
print(solution)