OJ Board

What is wrong in my code?
#include <iostream>
#include <stack>
#include <string>
#include <vector>

using namespace std;
int main()
{
int n,m,l=0,t1=0,licz=0,port=1;
stack<char> s,b;
string a;
cin>>n;
char t;
vector<char> v;
v.push_back(0);
for(int i=0;i<n;i++)
{licz=0;
cin>>m;
port=1 ...