#include<stdio.h>
#include<string.h>
#include<ctype.h>
#define MAX 100000
char stack[MAX];
int top=-1;
void push(char c){
    if(top<MAX-1){
        stack[++top]=c;
    }
}
char pop(){
    if(top>=0){
        return stack[top--];
    }
    return -1;
}
char peek(){
    if(top>=0)return stack[top];
    return -1;
}
int isOpening(char c){
    return (c=='('||c=='['||c=='{');
}
int isClosing(char c){
    return(c==')'||c==']'||c=='}');
}
int isMacthing(char open,char close){
    return ((open=='('&& close==')')||
    (open=='['&&close==']')||
    (open=='{'&&close=='}'));
}
int isAllowedChar(char c){
    return(isdigit(c)||c=='+'||c=='-'||c=='*'||c=='/'||
    c=='('||c==')'||c=='['||c==']'||
    c=='{'||c=='}'||isspace(c));
}
int isValidSequence(char *exp){
    int len=strlen(exp);
    for(int i=0;i<len;i++){
        char c=exp[i];
        if(!isAllowedChar(c)){
            return -1;
        }
        if(isOpening(c)){
            push(c);
        }
        else if(isClosing(c)){
            if(top== -1||!isMatching(pop(),c)){
                return 0;
            }
        }
    }
    if(top !=-1){
        return 0;
    }
    return 1;
}
int main(){
    char expression[MAX];
    if(!fgets(expression,sizeof(expression),stdin)){
        printf("Invalid input");
        return 0;
    }
    int result=isValidSequence(expression);
    if(result==-1){
        printf("Invalid input");
    }else if(result ==0){
        printf("Invalid sequence");
    }else{
        printf("Valid sequence");
    }
    return 0;
}