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OI-codes/S2OJ/11/11.cpp

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#include <bits/stdc++.h>
using namespace std;
int n, m, x, u, v, w, g[1005][1005], ans;
int main() {
cin >> n >> m >> x;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
g[i][j] = i == j ? 0 : 0x3f3f3f3f;
}
}
for (int i = 1; i <= m; i++) {
cin >> u >> v >> w;
g[u][v] = min(g[u][v], w);
}
for (int k = 1; k <= n; k++) {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
}
}
}
for (int i = 1; i <= n; i++) {
ans = max(ans, g[i][x] + g[x][i]);
}
cout << ans << endl;
return 0;
}