[plain]
#include
#include

int main()
{
int i;
int num;
int flag=1;
char a[100];

gets(a);
num=strlen(a);

if( (a[0]>='a' && a[0]<='z') || (a[0]>='A' && a[0]<='Z') || (a[0]=='_') )
{
for(i=1;i {
if((a[i]>='a' && a[i]<='z') || (a[i]>='A' && a[i]<='Z') || (a[i]>='0' && a[i]<='9') || (a[i]=='_') )
{
flag=1;
}
else
{
flag=0;
}
if(flag==0)
{
break;
}
}
if(flag)
{
printf("YES");
}
else
{
printf("NO");
}
}

else
{
printf("NO");
}

return 0;
}

#include
#include

int main()
{
int i;
int num;
int flag=1;
char a[100];

gets(a);
num=strlen(a);

if( (a[0]>='a' && a[0]<='z') || (a[0]>='A' && a[0]<='Z') || (a[0]=='_') )
{
for(i=1;i {
if((a[i]>='a' && a[i]<='z') || (a[i]>='A' && a[i]<='Z') || (a[i]>='0' && a[i]<='9') || (a[i]=='_') )
{
flag=1;
}
else
{
flag=0;
}
if(flag==0)
{
break;
}
}
if(flag)
{
printf("YES");
}
else
{
printf("NO");
}
}

else
{
printf("NO");
}

return 0;
}