Codeforces Round #386 (Div. 2), problem: (G) New Roads Solution in C/C++

Codeforces Round #386 (Div. 2), problem: (G) New Roads Solution in C/C++

#include<stdio.h>
#include<stdlib.h>
typedef unsigned u;
u D[222222],H[222222],P[222222],A[222222];
int main()
{
	u n,d,x,i=-1,j,k,mi=0,ma=1;
	for(scanf("%u%u%u",&n,&d,&x);++i<d;)scanf("%u",D+i);
	for(i=d;i--;ma+=D[i]-1)if(D[i]>D[i+1])mi+=D[i]-D[i+1];
	if(x<mi||x>ma){printf("-1\n");return 0;}
	for(A[i=0]=2;i++<d;)A[i]=A[i-1]+D[i-1];
	for(i=1;++i<A[1];)P[i]=1;
	for(i=0;++i<d;)
	{
		k=D[i-1]-1;
		if(k>D[i]-1)k=D[i]-1;
		j=ma-x;
		if(j>k)j=k;
		ma-=j;
		j=A[i]-1-j;
		for(k=A[i]-1;++k<A[i+1];)
		{
			P[k]=j;
			if(j+1<A[i])++j;
		}
	}
	for(printf("%u\n",A[d]-1);n>1;--n)printf("%u %u\n",n,P[n]);
	return 0;
}