参考答案：

#include<iostream>

using namespace std;

int main() 
{
	int y, m, d;

	scanf("%4d-%2d-%2d", &y, &m, &d);
	if (d > 2) printf("%d-%02d-%02d\n", y, m, d - 2);
	else
	{
		if (m == 3)
		{
			if (y % 4 == 0 && y % 100 != 0 || y % 400 == 0)
			{
				if (d == 1)
					printf("%d-%02d-28\n", y, m - 1);
				else
					printf("%d-%02d-29\n", y, m - 1);
			}
			else
			{
				if (d == 1)
					printf("%d-%02d-27\n", y, m - 1);
				else
					printf("%d-%02d-28\n", y, m - 1);
			}
		}
		else if (m == 1)
		{
			if (d == 1)
				printf("%d-12-30\n", y - 1);
			else printf("%d-12-31\n", y - 1);
		}
		else if (m == 7)
		{
			if (d == 1)
				printf("%d-%02d-29\n", y, m - 1);
			else printf("%d-%02d-30\n", y, m - 1);
		}
		else if (m == 8)
		{
			if (d == 1)
				printf("%d-%02d-30\n", y, m - 1);
			else printf("%d-%02d-31\n", y, m - 1);
		}
		else if (m == 5 || m == 10 || m == 12)
		{
			if (d == 1)
				printf("%d-%02d-29\n", y, m - 1);
			else printf("%d-%02d-30\n", y, m - 1);
		}
		else
		{
			if (d == 1)
				printf("%d-%02d-30\n", y, m - 1);
			else printf("%d-%02d-31\n", y, m - 1);
		}
	}

	return 0;
}

#include<iostream>

bool j(int y)
{
	return (y % 4 == 0 && y % 100 != 0) || y % 400 == 0;
}

void solve(int date[3])
{
	int they{date[0]}, them{date[1]}, tdby{date[2]};
	int m[13] = {29,
		31, 28, 31,
		30, 31, 30,
		31, 31, 30,
		31, 30, 31
	};
	if(tdby - 2 <= 0) {
		if(j(they) && them == 3) {
			tdby += m[0] - 2;
			them = 2;
		}
    else if(them == 1) {
			they--;
			them = 12;
			tdby += m[12] - 2;
		}
    else {
			them--;
			tdby += m[them] - 2;
		}
	}
  else {
		tdby -= 2;
	}
	printf("%d-%02d-%02d", they, them, tdby);
}

int main()
{
	int date[3];
	scanf(
		"%d-%d-%d",
		&date[0], &date[1], &date[2]
	);
	solve(date);
	return 0;
}