const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void (async function () {
const n = Number(await readline());
const lines = [];
for (let i = 0; i < n; i++) {
const [sousa, copyNum, num] = (await readline()).split(" ");
lines.push({ sousa, copyNum, num, index: i + 1 });
}
const copyKis = [[], [], [], [], []];
console.log(copyKis);
lines.forEach((line) => {
if (line.sousa == "IN") {
const copyKiNum = Number(line.copyNum);
const copyKi = copyKis[copyKiNum - 1];
copyKi.push([line.index, Number(line.num)]);
} else if (line.sousa == "OUT") {
const copyKiNum = Number(line.copyNum);
const copyKi = copyKis[copyKiNum - 1];
if (copyKi.length == 0) {
console.log(null);
} else {
copyKi.sort((a, b) => a[1] - b[1]);
const copy = copyKi.pop();
console.log(copy[0]);
}
}
});
})();