UVA_10963_The_Swallowing_Ground

#include <stdio.h>
int main()
{
    int i, n, y1, y2, T;
    scanf("%d", &T);
    while(T--){
        scanf("%d", &n);
        scanf("%d%d", &y1, &y2);
        int judge = 0, tmp = y1-y2;
        for(i = 1; i < n; i++){
            scanf("%d%d", &y1, &y2);
            if(y1-y2 != tmp)   judge = 1;
        }
        puts(judge?"no":"yes");
        if(T)   puts("");
    }
    return 0;
}