real.c

#include <stdio.h>
#define L 37

long f[L];
char g[L + 1];//  = 5827374;

int main() {
    int n;
    scanf("%d", &n);
    f[30] = 160;
    f[10] = 47;
    f[13] = 4;
    f[25] = 205;
    f[5] = 87;
    f[24] = 247;
    f[6] = 76;
    f[31] = 176;
    f[7] = 74;
    f[34] = 154;
    f[21] = 231;
    f[32] = 135;
    f[8] = 75;
    f[1] = 102;
    f[9] = 75;
    f[28] = 232;
    f[29] = 148;
    f[3] = 108;
    f[11] = 33;
    f[4] = 127;
    f[14] = 21;
    f[18] = 89;
    f[16] = 3;
    f[26] = 215;
    f[20] = 211;
    f[15] = 8;
    f[17] = 25;
    f[27] = 217;
    f[0] = 101;
    f[33] = 143;
    f[22] = 245;
    f[19] = 241;
    f[12] = 56;
    f[36] = 129;
    f[23] = 206;
    f[2] = 125;
    f[35] = 202;
    int m = n ^ 5827369, i;
    for (i = 0; i < L; ++i) {
        g[i] = f[i] ^ (i * m);
    }
    g[i] = 0;
    // hey that wasn't so hard!
    if (g[0] == 'e' && g[1] == 'a' && g[2] == 's' && g[3] == 'y' && g[4] == 'c' && g[5] == 't' && g[6] == 'f')
        printf("the flag is %s\n", g);
}