Arithmetic Expression cheak using Stack

#include<iostream>
#include <stack>
#include <stdio.h>
using namespace std;

int main()
{
    char exp[100];
    char valid[] = "1234567890+-*/()^";
    int i,x=0,y=0;
    stack <char> myStack;
    cout << "Input the Expression: ";
    gets(exp);
    for(i=0; exp[i] != '\0'; i++)
    {
        myStack.push(exp[i]);
    }
    while(!myStack.empty())
    {
        for(i=0; valid[i] != '\0'; i++)
        {
            if(myStack.top()==valid[i])
            {
               x =1;
            }
        }
        if(x==1)
        {
            myStack.pop();
            continue;
        }
        else
        {
            cout << "Invalid Arithmetic Expression"<<endl;
            y=1;
            break;
        }

    }
    if(y==0)
    {
       cout << "Valid Arithmetic Expression"<<endl;
    }

    return 0;
}