offer45--约瑟夫环

# coding=utf-8
def lastdelete(n,m):
    if n<1 and m<1:
        return -1
    index=0
    for i in range(1,n+1):
        index=(index+m)%i#f[i] = (f[i-1] + m) % i   约瑟环
    return index
if __name__ == '__main__':
    print(lastdelete(5,3))