Codeforces 1191C.cpp

#include <bits/stdc++.h>
#define pb push_back
#define pf push_front
#define pob pop_back
#define fp first
#define sp second
#define mp make_pair
#define ins insert
#define uEdge(u, v) g[u].pb(v), g[v].pb(u)
#define uwEdge(u, v, w) g[u].pb({v, w}), g[v].pb({u, w})
#define dEdge(u, v) g[u].pb(v)
#define dwEdge(u, v, w) g[u].pb({v, w})
#define BOOST ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define minHeap int, vector<int>, greater<int>
#define MOD 1000000007

using namespace std;
typedef long long int lli;
typedef pair<int, int> pii;
lli nl, arr[0];
vector<int> g[0];

lli gcd(lli a, lli b){if(b == 0) return a;a%=b;return gcd(b, a);}
lli lcm(lli a, lli b){return (a*b)/gcd(a, b);}
int bs(lli sum){int l=0,r=nl-1,mid;while(l<=r){mid=(l+r)/2;if(arr[mid]==sum)return mid;if(arr[mid]<sum)l=mid+1;else r=mid-1;}return -1;}
lli modPow(lli a, lli b){a%=MOD;lli ans=1;while(b > 0){if(b & 1) ans=ans*a%MOD;a=a*a%MOD;b>>=1;}return ans;}

int main(){
    lli n, m, k, tope, ans=0, deleted, pi;
    queue<lli> q;
    scanf("%lld %lld %lld", &n, &m, &k);
    for(int i = 1; i <= m; i++) scanf("%lld", &pi), q.push(pi);
    tope=k;
    if(q.front() > tope) tope=(q.front()/k+(q.front()%k!=0))*k;
    while(!q.empty()){
        ans++;
        deleted=0;
        while(!q.empty() && q.front() <= tope) deleted++, q.pop();
        tope+=deleted; 
        if(!q.empty() && q.front()-tope > 0) tope+=((q.front()-tope)/k+((q.front()-tope)%k!=0))*k;
        //q.front()-tope=desecha la pagina donde "tope" es el tope y ubica la pagina de q.front() como si fuera la primera
    }
    printf("%lld", ans);
    return 0;
}