#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
const int MAXN = 300005, Mo = 1000000007;
int n, s, x, m, a[MAXN], c[MAXN], z[MAXN], b[MAXN], f[MAXN];
int r() { return ((rand() << 16 | rand()) % n + n) % n + 1; }
int cmp(int i, int j) { return a[i] < a[j]; }
int main() {
  int* lx = new int[5];
  srand((unsigned long long)(lx));
  delete[] lx;
  n = read();
  s = read();
  x = read();
  if (n <= 1500) {
    int y, z = -1;
    while (s != -1) {
      printf("? %d\n", s);
      fflush(stdout);
      y = read();
      s = read();
      if (y >= x) {
        z = y;
        break;
      }
    }
    printf("! %d\n", z);
    fflush(stdout);
    return 0;
  }
  m = 0;
  memset(b, 0, sizeof(b));
  for (int i = (1); i <= (999); ++i) {
    int y = r();
    while (b[y]) y = r();
    b[y] = 1;
    printf("? %d\n", y);
    fflush(stdout);
    a[++m] = read();
    c[m] = read();
    z[m] = y;
  }
  printf("? %d\n", s);
  fflush(stdout);
  a[++m] = read();
  c[m] = read();
  z[m] = s;
  for (int i = (1); i <= (m); ++i) f[i] = i;
  sort(f + 1, f + 1 + m, cmp);
  if (c[f[m]] == -1 && a[f[m]] < x) {
    printf("! -1\n");
    fflush(stdout);
  } else if (a[f[1]] >= x) {
    printf("! %d\n", a[f[1]]);
    fflush(stdout);
  } else {
    for (int i = (1); i <= (m - 1); ++i)
      if (a[f[i]] < x && a[f[i + 1]] >= x) {
        if (a[f[i + 1]] == x) {
          printf("! %d\n", x);
          fflush(stdout);
          return 0;
        }
        int ans = a[f[i + 1]], y = c[f[i]], g;
        while (y != z[f[i + 1]]) {
          printf("? %d\n", y);
          fflush(stdout);
          g = read();
          y = read();
          if (g >= x) {
            ans = g;
            break;
          }
        }
        printf("! %d\n", ans);
        fflush(stdout);
        return 0;
      }
    int ans = -1, y = c[f[m]], g;
    while (y != -1) {
      printf("? %d\n", y);
      fflush(stdout);
      g = read();
      y = read();
      if (g >= x) {
        ans = g;
        break;
      }
    }
    printf("! %d\n", ans);
    fflush(stdout);
    return 0;
  }
  return 0;
}
