#include <stdio.h>
#include <math.h>
 
// 構造体の定義
typedef struct {
    int x;
    int y;
} Point;
 
// 距離計算関数
double distance(Point p1, Point p2) {
    return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y));
}
 
// 点Aと線分BCの最短距離を計算する関数
double shortestDistance(Point A, Point B, Point C) {
    // ベクトルの定義
    double ABx = B.x - A.x;
    double ABy = B.y - A.y;
    double BCx = C.x - B.x;
    double BCy = C.y - B.y;
 
    // 線分BCの長さ
    double BC_length = distance(B, C);
    if (BC_length == 0) return distance(A, B); // BとCが同じ点の場合
 
    // 線分BCに対する点Aの投影位置を計算
    double t = (ABx * BCx + ABy * BCy) / (BC_length * BC_length);
 
    if (t < 0) {
        // プロジェクションが線分BCの外側（点Bに近い）
        return distance(A, B);
    } else if (t > 1) {
        // プロジェクションが線分BCの外側（点Cに近い）
        return distance(A, C);
    } else {
        // プロジェクションが線分BCの内側
        Point projection = { B.x + t * BCx, B.y + t * BCy };
        return distance(A, projection);
    }
}
 
int main() {
    Point A, B, C;
 
    // ユーザーからの入力
    printf("点Aの座標を入力してください (x y): ");
    scanf("%d %d", &A.x, &A.y);
    printf("点Bの座標を入力してください (x y): ");
    scanf("%d %d", &B.x, &B.y);
    printf("点Cの座標を入力してください (x y): ");
    scanf("%d %d", &C.x, &C.y);
 
    // 最短距離の計算
    double distance = shortestDistance(A, B, C);
    printf("点Aと線分BCの最短距離は: %.2f\n", distance);
 
    return 0;
}
 

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