#include <stdio.h>
int main()
{
    int N, M;
    scanf("%d%d",&N,&M);
    long int res;
    if (N <= M)
        res = 2 * (N - 1);
    else
        res= 2 * (M - 1)+1;
    printf("\n%d",res);
    return 0;
}

Can't solve this promlem myself.
I run your code online on some tests, it seemed ok.
Check, maybe you go out of range in res? (know nothing about C)

Here is the solution
http://xoptutorials.com/index.php/2017/01/01/timus1224/