#include <stdlib.h>
#include <string.h>
#include <stdio.h>
int main(int argc, char **argv) {
    size_t mb = argc > 1 ? (size_t)atol(argv[1]) : 3600;
    size_t n = mb * 1024 * 1024;
    char *p = malloc(n);
    if (!p) { perror("malloc"); return 1; }
    for (size_t i = 0; i < n; i += 4096) p[i] = (char)(i >> 12);
    printf("touched %zu MB\n", mb);
    sleep(30);
    return 0;
}