Problem:
Score : 300 points

Problem Statement

There are N people standing in a row from west to east.
Each person is facing east or west.
The directions of the people is given as a string S of length N.
The i-th person from the west is facing east if S_i = E, and west if S_i = W.

You will appoint one of the N people as the leader, then command the rest of them to face in the direction of the leader.
Here, we do not care which direction the leader is facing.

The people in the row hate to change their directions, so you would like to select the leader so that the number of people who have to change their directions is minimized.
Find the minimum number of people who have to change their directions.

Constraints

2 \leq N \leq 3 \times 10^5

|S| = N

S_i is E or W.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of people who have to change their directions.

Sample Input 1

5
WEEWW

Sample Output 1

1

Assume that we appoint the third person from the west as the leader.
Then, the first person from the west needs to face east and has to turn around.
The other people do not need to change their directions, so the number of people who have to change their directions is 1 in this case.
It is not possible to have 0 people who have to change their directions, so the answer is 1.

Sample Input 2

12
WEWEWEEEWWWE

Sample Output 2

4

Sample Input 3

8
WWWWWEEE

Sample Output 3

3

Solution in JavaScript (node.js v5.12) (judge verdict: Accepted)

var lines = []; var ans = Infinity;
var readline = require('readline');

var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.on('line', function (x) {
    lines.push(x);
})

rl.on('close', function () {
    var N = Number(lines[0]);
    var S = lines[1].split("");

    // 一番左端の人がリーダだったケースを考える
    // 東向いている人は，全員西向きにする
    var result = 0;
    for (var string of S) { result += (string === "E" ? 1 : 0) }

    // リーダを変えて考える．リーダを東向きに一人ずつずらしていく
    for (var i = 0; i < N; i++) {
        // 一つ前のリーダが西を向いていたら，方向を変える人が1人増える
        result += (S[i - 1] === "W" ? 1 : 0)

        // 現在のリーダーがが東を向いていたら，方向を変える人間が1人減る
        result -= (S[i] === "E" ? 1 : 0)

        ans = Math.min(ans, result);
    }

    console.log(ans);

});