AtCoder Beginner Contest 019 B - 高橋くんと文字列圧縮

from itertools import groupby

S=list(input())

ans=""
for k,g in groupby(S):
    moji=list(g)
    kosu=len(moji)
    char=moji[0]
    ans+=str(char)+str(kosu)

print(ans)