C :

#include<stdio.h>
#include<stdlib.h>

typedef struct tagNODE
{
	int num;
	int rec;
	struct tagNODE *next;
}node,*linklist;

void monkeylink(int n,linklist *head)
{
	linklist temp,upd;
	int i;
	(*head)=(linklist)malloc(sizeof(node));
	upd=(*head);
	for(i=1;i<=n;i++)
	{
		temp=(linklist)malloc(sizeof(node));
		temp->num=i;
		temp->rec=1;
		upd->next=temp;
		temp->next=NULL;
		upd=temp;
	}
	temp->next=(*head)->next;
}

int cnt(linklist head, int m)
{
	linklist temp;
	int i;
	temp=head;
	while(temp->next!=temp)
	{
		for(i=1;i<=m-1;i++)
			temp=temp->next;
		temp->next=temp->next->next;
	}
	return temp->num;
}
int main()
{
	int n,m;
	linklist monkey,head;
	scanf("%d%d",&n,&m);
	monkeylink(n,&head);
	printf("%d",cnt(head,m));
	return 0;
}

C++ :

#include <iostream>
using namespace std;
int main() {
    int m, n;
    scanf("%d %d", &n, &m);
    int index = 0;
    for (int i = 2; i <= n; ++i)
        index = (index + m) % i;
    printf("%d\n", index + 1);
    return 0;
}