

const { count } = require("console");
const fs = require("fs");
const { nextTick } = require("process");
const filePath = process.platform === "linux" ? "/dev/stdin" : "./예제.txt";
let input = fs.readFileSync(filePath).toString().trim();
// const fs = require('fs');
// let input = fs.readFileSync("/dev/stdin").toString().trim();
input = input.split('\n')
const n=+input.shift();
let levels=input.map((el)=>+el)
let counts=0;
for (let i=n-1;i>=1;i--){
if (levels[i]<=levels[i-1]){
counts+=(levels[i-1]-(levels[i]-1))
levels[i-1]=levels[i]-1
}
}
console.log(counts)
훌륭한 글이네요. 감사합니다.