#include<vector>
#include<stack>
#include<iostream>
int main()
{
    int noOfInstructions = 0;
    std::cin>> noOfInstructions;

    std::vector< std::stack< int > > myVectorOfStacks;
    myVectorOfStacks.reserve( 1001 );
    for( int inx = 0; inx < 1001; ++inx )
    {
         myVectorOfStacks.push_back( std::stack<int>() );
    }

    char instruction[3];
    int stackNumber = 0;
    int stackValue = 0;

    for( int inx = 0; inx < noOfInstructions; ++inx )
    {
        std::cin>> instruction;

        std::cin>> stackNumber;
        std::stack< int > & tempStack = myVectorOfStacks.at( stackNumber );

        if( instruction[1] == 'U' )
        {
            std::cin>> stackValue;
            tempStack.push( stackValue );
        }
        else
        {
             std::cout<< tempStack.top()<< "\n";
             tempStack.pop();
        }
    }

    return 0;
}