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#include <bits/stdc++.h> | |
#define mp make_pair | |
#define F first | |
#define S second | |
using namespace std; | |
typedef long long ll; | |
typedef long double ld; | |
using pll = pair<ll, ll>; | |
pll operator+(pll a, pll b){ | |
return mp(a.F + b.F, a.S + b.S); | |
} | |
pll operator-(pll a, pll b){ | |
return mp(a.F - b.F, a.S - b.S); | |
} | |
ll cross(pll a, pll b){ | |
return a.F * b.S - a.S * b.F; | |
} | |
ld dis(pll a, pll b){ | |
ll x = a.F - b.F, y = a.S - b.S; | |
return sqrt(x * x + y * y); | |
} | |
ld absv(pll v){ | |
return sqrt(v.F * v.F + v.S * v.S); | |
} | |
int main(){ | |
ios_base::sync_with_stdio(false); | |
cin.tie(0); | |
ll x, y, n; | |
cin >> x >> y >> n; | |
pll a = mp(x, y); | |
pll c; | |
cin >> c.F >> c.S; | |
ld ans = dis(a, c); | |
for(int i = 1; i <= n; i++){ | |
pll d; | |
cin >> d.F >> d.S; | |
pll cd = d - c; | |
pll v = mp(cd.S, -cd.F); | |
pll ca = a - c; | |
ld len = (ld)cross(ca, cd) / cross(cd, v); | |
ld px = a.F + len * v.F; | |
ld py = a.S + len * v.S; | |
ll mnx = min(c.F, d.F), mxx = max(c.F, d.F); | |
ll mny = min(c.S, d.S), mxy = max(c.S, d.S); | |
if(mnx <= px && px <= mxx && mny <= py && py <= mxy) | |
ans = min(ans, abs(len) * absv(v)); | |
ans = min(ans, dis(a, d)); | |
c = d; | |
} | |
cout << fixed << setprecision(20) << ans << "\n"; | |
return 0; | |
} |
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