# [Compiler Design] Mathematical Expression Validation

#include <bits/stdc++.h>
using namespace std;
int main()
{
long long int j,k,l,n,m,valid=0;
string s;
while(cin>>s)
{
valid=0;
l=s.length()-1;
for(j=1;j<s.length();j++)
{
if(s[0]>='a' && s[0]<='z' ||s[0]>='A' && s[0]<='Z'|| s[0]>='0' && s[0]<='9' ||s[0]=='(')
{
if(s[j]=='+' ||s[j]=='-'||s[j]=='*'||s[j]=='/'||s[j]=='='||s[j]=='>'||s[j]=='<'||s[j]=='^')
{
if((s[j-1]>='a' && s[j-1]<='z'||s[j-1]>='A' && s[j-1]<='Z' || s[j-1]>='0' && s[j-1]<='9')&&(s[j+1]>='a' && s[j+1]<='z' ||s[j+1]>='A' && s[j+1]<='Z'|| s[j+1]>='1' && s[j+1]<='9'))
{

valid=1;
}

else
{
if(s[0]=='(')
{
if(s[j-1]==')')
{

valid=1;
}
}
else
{
valid=0;
}

}
if(s[j+1]=='+' ||s[j+1]=='-'||s[j+1]=='*'||s[j+1]=='/'||s[j+1]=='='||s[j+1]=='>'||s[j+1]=='<'||s[j+1]=='^')
{

valid=0;
}

}
else if(s[j]=='(' )
{
if(s[j-1]=='+' ||s[j-1]=='-' ||s[j-1]=='*'||s[j-1]=='/' ||s[j-1]=='^')
{
valid=1;
}
else
{
valid=0;
}
if((s[j+1]>='a' && s[j+1]<='z')||s[j+1]>='A' && s[j+1]<='Z'||(s[j+1]>='0' && s[j+1]<='9'))
{
valid=1;
}
else
{
valid=0;
}
}
else if(s[j]==')' )
{
if(s[j+1]=='+' ||s[j+1]=='-' ||s[j+1]=='*'||s[j+1]=='/' ||s[j+1]=='^' ||s[j+1]=='/0')
{
if(s[j+2]!='+' ||s[j+2]!='-' ||s[j+2]!='*'||s[j+2]!='/' ||s[j+2]!='^' ||s[j+2]!='/0')
{
valid=1;
}

}
else
{
valid=0;
}
if((s[j-1]>='a' && s[j-1]<='z')||s[j-1]>='A' && s[j-1]<='Z'||(s[j-1]>='0' && s[j-1]<='9'))
{
valid=1;
}
else
{
valid=0;
}
}
if(s[l]=='+' ||s[l]=='-' ||s[l]=='*'||s[l]=='/' ||s[l]=='^' ||s[l]=='/0')
{
valid=0;
}

}
}
if(valid==1)
{
cout<<"Valid"<<endl;
}
else
{
cout<<"Invalid"<<endl;
}
}

return 0;
}