#include<stdio.h>
#include<string.h>
#include<ctype.h>
const char keyword[32][10] =
{
	"int","float","double","char","short","long","signed","unsigned",
	"void","auto","register","static","extern","typedef","if","else",
	"switch","case","default","for","while","do","break","continue",
	"goto","return","const","union","struct","enum","volatile","sizeof"
};
int main()
{
	char s[53];
	while (gets(s) != NULL)
	{
		int jud = 1;
		for (int i = 0; i < 32; i++)
		{
			if (!strcmp(s, keyword[i]))
			{
				jud = 0;
			}
		}
		int len = strlen(s);
		if (s[0]>='0'&&s[0]<='9')
			{
				jud = 0;
			}
		for (int i = 0; i < len && jud == 1; i++)
		{
			 
			if (!((s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z') ||s[i] == '_'))
			{
				jud = 0;
			}
		}
		if (jud == 1)
		{
			printf("Yes\n");
		}
		else
		{
			printf("No\n");
		}
	}
	
	return 0;
}

注意：因为使用了gets函数，所以很多情况下可能无法运行