#include <iostream> #include <string> using namespace std; bool isRunnian(int year){ return year%400==0||year%4==0&&year%100!=0; } int sumDay(int year1,int month1,int day1,int year2 , int month2, int day2){ int dayOfMonth[]={0,31,28,31,30,31,30,31,31,30,31,30,31}; int day=0; for(...