##R, 97 bytes

if(all((a=scan())==a[1])){a=c(a,1)}else{while(!all(a==a[1])){a[which(a==min(a))][1]=min(a)+1}};a

Too bad that the synthax x=+1 doesn't exist in R !

Ungolfed :

if(all((a=scan())==a[1]))
{
    a=c(a,1)
}
else
{
    while(!all(a==a[1]))
    {
        a[which(a==min(a))][1]=min(a)+1
    }
a

R, 97 bytes

if(all((a=scan())==a[1])){a=c(a,1)}else{while(!all(a==a[1])){a[which(a==min(a))][1]=min(a)+1}};a

Too bad that the synthax x=+1 doesn't exist in R !

Ungolfed :

if(all((a=scan())==a[1]))
{
    a=c(a,1)
}
else
{
    while(!all(a==a[1]))
    {
        a[which(a==min(a))][1]=min(a)+1
    }
a