#include<stdio.h>
int main(){
int n;
scanf(“%d”,&n);
if(n <= 5)
printf(“-1\n”);
else{
printf(“1 2\n2 3\n2 4\n”);
for(int i = 5;i <= n;i++)
printf(“1 %d\n”,i);
}
for(int i = 2;i <= n;i++)
printf(“1 %d\n”,i);
}
Codeforces Round #473 (Div. 2), problem: (C) Mahmoud and Ehab and the wrong algorithm Solution In C/C++
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