简单题
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#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;
#define maxn 1005
int f[maxn];
int n;
bool vis[maxn];
int gcd(int x, int y)
{
if (!x || !y)
return x > y ? x : y;
for (int t; t = x %y; x = y, y = t);
return y;
}
int main()
{
//freopen("t.txt", "r", stdin);
scanf("%d", &n);
for (int i = 0; i< n; i++)
{
int a;
scanf("%d", &a);
a--;
f[a] = i;
}
memset(vis, 0, sizeof(vis));
int ans = 1;
for (int i = 0; i < n; i++)
if (!vis[i])
{
int a = i;
int b = 0;
while (!vis[a])
{
vis[a] = true;
a = f[a];
b++;
}
ans = ans / gcd(ans, b) * b;
}
printf("%d\n", ans);
return 0;
}