const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void (async function () {
const memories = Array.from({ length: 100 }, () => 0);
const helper = (num) => {
let left = memories.indexOf(0);
let right = memories.indexOf(0);
while (right < memories.length) {
left = right;
while (memories[right] == 0) {
right++;
}
if (right - left >= num) {
return left;
}
right++;
}
return -1;
};
let ans = [];
let allocated = [];
const n = Number(await readline());
for (let i = 0; i < n; i++) {
const [cmd, num] = (await readline()).split("=");
if (cmd == "REQUEST") {
const index = helper(Number(num));
if (index == -1) {
ans.push("error");
} else {
for (let i = index; i < index + Number(num); i++) {
memories[i] = 1;
allocated.push({ startIndex: index, size: Number(num) });
}
ans.push(index);
}
} else {
const target = allocated.filter((item) => item.startIndex == Number(num));
if (target.length == 0) {
ans.push("error");
} else {
for (let i = target[0].startIndex; i < target[0].size; i++) {
memories[i] = 0;
}
}
}
}
for (let i = 0; i < ans.length; i++) {
console.log(ans[i]);
}
})();