B747 CREW CROSSED AN ACTIVE RWY WITHOUT CLRNC.

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ACR FLT XX WAS TO DEPART SFO-NRT AT XA25Z FOR A SLOT TIME OF XA51Z. PUSHBACK WAS DELAYED FOR INBOUND COMPANY TFC. THEN AFTER PUSHING BACK WE WERE ASKED TO PULL FORWARD TO LET ACR A GET BY ON TXWY A. WE PULLED FORWARD THEN PUSHED BACK WHEN TFC WAS CLR. AFTER ENG START WE REQUESTED OUR TAXI CLRNC. WE WERE TOLD TO TAXI TO RWY 28R VIA TXWY F; HOLD SHORT OF RWY 1L AND HOLD FOR AN ACR A ACFT. THE CLRNC WAS CONFUSING BECAUSE ACR B AND ACR A WERE ON TXWY A PAST TXWY F AND WE WERE ON TXWY A IN FRONT OF TXWY F. WE SHOULD HAVE BEEN TOLD TO HOLD SHORT OF TXWY F; ETC. WHEN ACR A WENT BY US THERE WAS VERY LITTLE WINGTIP CLRNC. THIS CAUSED OUR ATTN TO BE DIVERTED TO ACFT SEPARATION. WE THEN TAXIED ON TXWY F AND HELD SHORT OF RWY 1L. WE WERE THEN GIVEN THE CLRNC TO CROSS RWY 1L AND HOLD SHORT OF RWY 1R. WE STARTED ACROSS RWY 1L AND I THOUGHT THE CAPT WAS GOING TO HOLD SHORT OF RWY 1R. THE SUN WAS BRIGHT WITH THE HAZE COMING THROUGH MY SIDE WINDOW. GETTING BEHIND ON OUR SLOT TIME AND NEW RWY DEP I TOOK A MOMENT TO CHK THE 10-7 PAGES; TO CHK FOR NONSTANDARD CLEANUP ALT; DEP SID; CLOSE-IN NOISE ABATEMENT. THE CAPT THEN ASKED ABOUT CONTINUING OUR TAXI. AT THAT TIME I BECAME AWARE WE HAD CROSSED RWY 1R. (AT NO TIME WAS GND CTL BUSY WITH OTHER TFC AND THEY DID NOT ADVISE US TO HOLD SHORT OF RWY 1R WHEN IT BECAME OBVIOUS WE WERE NOT STOPPING.) GND THEN SAID SOMETHING TO THE EFFECT THAT YOU MIGHT AS WELL CONTINUE TAXIING NOW. WE THEN FINISHED TAXIING AND TOOK OFF WITHOUT FURTHER INCIDENT.