URAL 1010 Discrete Function

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int N, f;
long long ans, x, px;
int main()
{
    int i;
    while(scanf("%d", &N) == 1)
    {
        ans = -1;
        scanf("%lld", &px);
        for(i = 1; i < N; i ++)
        {
            scanf("%lld", &x);
            if(llabs(x - px) > ans)
                ans = llabs(x - px), f = i;
            px = x;
        }
        printf("%d %d\n", f, f + 1);
    }
    return 0;
}