#include <stdio.h> #include <malloc.h> char str[60000]; int str_len = 0; /// <summary> /// グローバル変数strの中身を入力された文字列で上書きする /// </summary> void ReadString() { char c = getchar(); str_len = 0; while (c != '\n') { str[str_len] = c; c = getchar(); str_len++; } } /// <summary> /// 入力された数字を返す /// </summary> /// <returns></returns> int ReadNum() { int negate = 0; char c = getchar(); int num = 0; int numCnt = 0; while (c != '\n') { if (c == '-') { negate = 1; } else { num = num * 10 + c - '0'; } c = getchar(); } if (negate == 1) { num *= -1; } return num; } /// <summary> /// ReadStringの文字列のうち、スペースで区切られた左側か右側を取得する /// </summary> /// <param name="leftIs">左が欲しければtrue,右ならfalse</param> /// <returns>引数に対応した側の数字を返す</returns> int GetLR(int leftIs) { int cnt = 0; int num = 0; int left = 0; int right = 0; while (1) { if (cnt >= str_len) { right = num; break; } if (str[cnt] == ' ') { left = num; num = 0; cnt++; continue; } num = num * 10 + (str[cnt] - '0'); cnt++; } if (!leftIs) { return left; } else { return right; } } int getWafu() { int n = ReadNum() - 1; ReadString(); if (GetLR(1) - GetLR(0) < 0) return -1; int ans = GetLR(1) - GetLR(0); int wafu = ans; for (int i = 0;i < n;i++) { ReadString(); if (GetLR(1) - GetLR(0) != ans) wafu = -1; } return wafu; } int main() { printf("%d\n",getWafu()); }