Find a Position in a Genome Minimizing the Skew

a=input()d={}c,g,m=0,0,0for i in range(len(a)):    if a[i]=='C':        c+=1    elif a[i]=='G':        g+=1    d[i]=g-c #用字典保存每个i前缀g和c的个数差值    if d[i]<m: #用m保存最小的i值        m=d[i]for key in d.keys():    if d[key]==m:        print(key+1,end=" ") #因为前缀的下标是从0开始的，对应到字符串上应该+1