鸡兔同笼 n为总数，m为总腿数，a为鸡，b为兔

#include<stdio.h>
int main()
{
 	int m,n,a,b;
    scanf("%d%d",&n,&m);
    if(m>=2*n&&m%2==0)  //满足该式子必定有解
    {
    	a=(4*n-m)/2;
    	b=(m-2*n)/2;
    	printf("%d %d",a,b);
	}
	else
	{
		printf("No");
	}
    return 0;
 }